nervous system
It is composed of the brain, the spinal cord and enormous network of nerves that thread throughout the body.
nervous system
Basic Functions of the Nervous System
Sensation
Integration
Motor output
gathering information
To monitor changes occurring inside and outside the body
Such changes are known as stimuli and the cells that monitor them are
receptors.
sensation
to process and interpret sensory input and decide if action is needed.
integration
A response to integrated stimuli
The response activates muscles or glands
motor output
Two Main Division of Nervous System
1. Central nervous system (CNS)
2. Peripheral nervous system (PNS)
Brain
Spinal cord
Central nervous system (CNS)
Nerve outside the brain and spinal cord (e.g. spinal nerves, cranial nerves)
Responsible for communication between the CNS and the rest of the body.
Peripheral nervous system (PNS)
The Peripheral nervous system (PNS) can be divided into:
1. Sensory (afferent) Division
2. Motor (efferent) Division
Conducts impulses from receptors to the CNS
Sensory nerve fibers can be somatic (from skin, skeletal muscles or joints) or visceral (from organs w/i the ventral body cavity)
Sensory (afferent) Division
Nerve fibers that carry impulses away from the CNS
Motor (efferent) Division
The Motor (efferent) Division can be divided further:
1. Somatic nervous system
2. Autonomic nervous system
VOLUNTARY (generally)
Somatic nerve fibers that conduct impulses from the CNS to skeletal muscles
somatic nervous system
INVOLUNTARY (generally)
Conducts impulses from the CNS to smooth muscle, cardiac muscle, and glands.
autonomic nervous system
The Autonomic Nervous System can be divided into:
1. Sympathetic Nervous System
2. Parasympathetic Nervous System
Responsible for our “Fight or Flight” reactions
sympathetic nervous system
Activated during “Rest and Digestion”
parasympathetic nervous system
Sympathetic Nervous System
Responsible for our “Fight or Flight” reactions such as
Increased Heart Rate
Increased Blood Pressure
Pupil Dilation
Decreased Urination
Increased Sweating
Bronchial Dilation
Decreased Salivation
Penile ejaculation
Parasympathetic Nervous System
Activated during “Rest and Digestion” such as
Decreased Heart Rate
Decreased Blood Pressure
Pupil Constriction
Increased Urination
Decreased Sweating
Bronchial Constriction
Increased Salivation
Increased GI secretions and peristalsis
Penile erection
it is the functional and structural unit of the nervous system
neuron
Major regions of neurons
1. Cell body
2. Processes
2.1 Dendrites
2.2 Axons
nucleus and metabolic center of the cell
Cell body
fibers that extend from the cell body (dendrites and axons)
Processes
conduct impulses toward the cell body
Dendrites
conduct impulses away from the cell body (only 1!)
Axons
The specialized glial cells that wrap around the axon of neurons.
Myelin Sheath
Myelin Sheath – The specialized glial cells that wrap around the axon of neurons. This is made by:
Within the CNS Oligodendrocytes
Within the PNS Schwann Cells
Within the CNS _________
Oligodendrocytes
Within the PNS ___________
Schwann Cells
the gaps in myelin sheath along the axon
Nodes of Ranvier
Myelinization __________________ of nerve conduction
increase the speed
What’s the Matter?
(white vs grey matter)
composed of non-myelinated fibers and cell bodies
Grey Matter
composed of Myelinated neurons
Brain – Grey matter covers white matter
Spinal Cord – White matter covers grey matter
White Matter
Grey matter covers white matter
Brain
White matter covers grey matter
Spinal Cord
Functional Classification of Nuerons
1. Sensory (afferent) neurons
2. Motor (efferent) neurons
3. Interneurons (association neurons)
Carry impulses from the sensory receptors to CNS ( e.g. Cutaneous sense organs, Proprioceptors – detect stretch or tension)
Sensory (afferent) neurons
Carry impulses away from the CNS to the effector organ (e.g muscles)
Motor (efferent) neurons
Found in neural pathways in the central nervous system
Connect sensory and motor neurons
Interneurons (association neurons)
Characteristics of a Neuron
1. irritability
2. conductivity
ability to respond to stimuli
Irritability
ability to transmit an impulse
Conductivity
Starting a Nerve Impulse
Depolarization
The Action Potential (Nerve Impulse)
Action Potential (Nerve Impulse) Propagation
Continuation of the Nerve Impulse between Neurons
a stimulus depolarizes the neuron’s membrane
A depolarized membrane allows sodium (Na+) to flow inside the membrane (Na influx) The exchange of ions initiates an action potential in the neuron
Depolarization
If the action potential (nerve impulse) starts, it is propagated over the entire axon
Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane
The sodium-potassium pump restores the original configuration This action requires ATP
The Action Potential (Nerve Impulse)
The impulse continues to move toward the cell body
Impulses travel faster when fibers have a myelin sheath
o Myelinated neurons conduct nerve impulses faster
Action Potential (Nerve Impulse) Propagation
Impulses are able to cross the synapse to another nerve by the help neurotransmitter: Neurotransmitter is released from a nerve’s axon terminal
The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter
An action potential is started in the dendrite
Continuation of the Nerve Impulse between Neurons
-The largest division of the brain (more than half of the brain mass). It is divided into two hemispheres (left and right), each of which is divided into four lobes.
Frontal
Parietal
Occipital
Temporal
Cerebral Hemispheres (Cerebrum)
Cerebral Hemispheres (Cerebrum) -The largest division of the brain (more than half of the brain mass). It is divided into two hemispheres (left and right), each of which is divided into four lobes.
frontal lobe
parietal lobe
occipital lobe
temporal lobe
- The outermost layer of gray matter making up the superficial aspect of the cerebrum.
Cerebral Cortex
Cerebral Features:
• Gyri (Gyrus: singular)
• Sulci (Sulcus: singular)
• Central Sulcus
• Fissures
• Longitudinal Fissure
• Transverse Fissure
• Sylvian/Lateral Fissure
– Elevated ridges “winding” around the brain.
Gyri (Gyrus: singular)
– Small grooves dividing the gyri
Sulci (Sulcus: singular)
– Divides the Frontal Lobe from the Parietal Lobe
• Central Sulcus
– Deep grooves, generally dividing large regions/lobes of the brain
Fissures
– Divides the two Cerebral Hemispheres
Longitudinal Fissure
– Separates the Cerebrum from the Cerebellum
Transverse Fissure
– Divides the Temporal Lobe from the Frontal and Parietal Lobes
Sylvian/Lateral Fissure
lobes of the brain:
frontal lobe
parietal lobe
occipital lobe
temporal lobe
located deep to the Frontal Bone of the skull.
It plays an integral role in the following functions/actions: Memory Formation
Emotions
Decision making/reasoning
Personality
Frontal lobe
Frontal Lobe - Cortical Regions
• Primary Motor Cortex (Precentral Gyrus)
• Broca’s Area
• Broca’s Aphasia
– Cortical site involved with controlling
movements of the body.
Primary Motor Cortex (Precentral Gyrus)
– Controls facial neurons, speech, and language comprehension. Located on Left Frontal Lobe.
Broca’s Area
– Results in the ability to comprehend speech, but the decreased motor ability (or inability) to speak and form words.
Broca’s Aphasia
located deep to the Parietal Bone of the skull.
It plays a major role in the following functions/actions:
- Senses and integrates sensation(s)
- Spatial awareness and perception
(Proprioception - Awareness of body/ body parts in space and in relation to each other)
Parietal Lobe
Parietal Lobe - Cortical Regions
Primary Somatosensory Cortex (Postcentral Gyrus)
Somatosensory Association Cortex
Primary Gustatory Cortex
– Site involved with processing of tactile and proprioceptive information.
Primary Somatosensory Cortex (Postcentral Gyrus)
- Assists with the integration and interpretation of sensations relative to body position and orientation in space. May assist with visuo- motor coordination.
Somatosensory Association Cortex
– Primary site involved with the interpretation of the sensation of Taste.
Primary Gustatory Cortex
located deep to the Occipital Bone of the Skull.
Its primary function is the processing, integration, interpretation, etc. of VISION and visual stimuli.
Occipital Lobe
Occipital Lobe - Cortical Regions
Primary Visual Cortex
Visual Association Area
– This is the primary area of the brain responsible for sight - recognition of size, color, light, motion, dimensions, etc.
Primary Visual Cortex
– Interprets information acquired through the primary visual cortex.
Visual Association Area
located on the sides of the brain, deep to the Temporal Bones of the skull. They play an integral role in the following functions:
• Hearing
• Organization/Comprehension of language
• Information Retrieval (Memory and Memory Formation)
Temporal Lobe
Temporal Lobe – Cortical Regions
Primary Auditory Cortex
Primary Olfactory Cortex
Wernicke’s Area
– Responsible for hearing
Primary Auditory Cortex
– Interprets the sense of smell once it reaches the cortex
via the olfactory bulbs. (Not visible on the superficial cortex)
Primary Olfactory Cortex
– Language comprehension. Located on the Left Temporal Lobe.
Wernicke’s Area
– Language comprehension is inhibited. Words and sentences
are not clearly understood, and sentence formation may be inhibited or non-sensical.
is a language disorder that affects the ability to understand and produce meaningful speech. It is caused by damage to the Wernicke's area in the brain, which is responsible for language comprehension.
Wernicke’s Aphasia
- A white matter tract that connects Broca’s Area and Wernicke’s Area through the Temporal, Parietal and Frontal Lobes. Allows for coordinated, comprehensible speech. Damage may result in:
Arcuate Fasciculus
- Where auditory comprehension and speech articulation are preserved, but people find it difficult to repeat heard speech.
Conduction Aphasia
- Attaches to the spinal cord
The Brain Stem
Parts of the brain stem:
Midbrain
Pons
Medulla oblongata
-Mostly composed of tracts of nerve fibers
Reflex centers for vision and hearing
Cerebral aquaduct – 3rd-4th ventricles
The midbrain
The bulging center part of the brain stem
Mostly composed of fiber tracts
Includes nuclei involved in the control of breathing
Pons
o The lowest part of the brain stem o Merges into the spinal cord
o Includes important fiber tracts
o Contains important control centers
Heart rate control
Blood pressure regulation
Breathing
Swallowing
Vomiting
Medulla Oblongata
Composed of two hemispheres with convoluted surfaces below the cerebrum
Provides involuntary coordination of body movements
The Cerebellum
Protection of the Central Nervous System:
Scalp and skin
Skull and vertebral column
Meninges
Cerebrospinal fluid
The Meninges
1. Dura matter
2. Arachnoid layer
3. Pia mater
Double-layered external covering
Periosteum – attached to surface of the skull
Meningeal layer – outer covering of the brain
Dura matter
– attached to surface of the skull
Periosteum
– outer covering of the brain
Meningeal layer
-Middle layer
Arachnoid layer
- Internal layer
- Clings to the surface of the brain
Pia mater
The space between the arachnoid and the pia matter ____________________ is filled with Cerebspinal fluid
(subarachnoid space)
Similar to blood plasma composition (hence, has been regarded as an ultrafiltrate of the blood plasma)
In a man the total volume of CSF has been estimated to be about 140 ml
Formed by the choroid plexus
Forms a watery cushion to protect the brain
Circulated in arachnoid space, ventricles, and central canal of the spinal cord
The Cerebrospinal Fluid
A long cylindrical structure invested by meninges, which lies in the vertebral canal.
Extends from foramen magnum (opening at the base of the skull) to the region of
between L1 and L2
31 spinal nerves sprout from the spinal cords
8 cervical nerves
12 thoracic nerves
5 lumbar nerves
5 sacral nerves
1 coccygeal nerve
The Spinal Cord
= bundle of neuron fibers
Neuron fibers are bundled by connective tissue
Nerve
-are nerves that emerge directly from the brain, in contrast to spinal nerves which emerge from segments of the spinal cord.
Cranial nerves
In humans, there are ______ pairs of cranial nerves.
12
smell
I. Olfactory
vision
II. Optic
eyelid and eyeball movement
III. Oculomotor
innervates superior oblique
turns eye downward and laterally
IV. Trochlear
chewing
face & mouth touch & pain
V. Trigeminal
turns eye laterally
VI. Abducens
controls most facial expressions secretion of tears & saliva
taste
VII. Facial
(auditory) hearing
equillibrium sensation
VIII. Vestibulocochlear
taste
senses carotid blood pressure
IX. Glossopharyngeal
senses aortic blood pressure
slows heart rate
stimulates digestive organs taste
X. Vagus
controls trapezius & sternocleidomastoid
controls swallowing movements
XI. Spinal Accessory
controls tongue movements
XII. Hypoglossal
is an egg-shaped structure lies above your brainstem in the middle of the brain. Although it may look like a single structure, you actually have two, side-by-side thalami, one in each hemisphere (side) of your brain. Being located in this central area — like the central hub on a bike wheel — allows nerve fibers connections (like the bike wheel’s spokes) to reach all areas of your cerebral cortex (the outer layer of your brain).
Technically, your thalamus is part of an area of your brain called the diencephalon, which includes your hypothalamus, subthalamus and epithalamus.
thalamus
Technically, your thalamus is part of an area of your brain called the__________________, which includes your hypothalamus, subthalamus and epithalamus.
diencephalon
Diencephalon
- Thalamus
- Hypothalamus
- Subthalamus
- Epithalamus
AN
Anterior nucleus
IML
Internal medullary lamina
DM
Dorsomedial nucleus
LD
Lateral dorsal nucleus
LP
Lateral posterior nucleus
P
Pulvinar nucleus
VA
Ventral anterior nucleus
VL
Ventrolateral nucleus
VPM
Ventral posteromedial nucleus
VPL
Ventral posterolateral nucleus
MG
LG
Medial geniculate nucleus
Lateral geniculate nucleus
R
Reticular nucleus
It’s known as a ______________________ of all incoming motor (movement) and sensory information — hearing, taste, sight and touch (but not smell) — from your body to your brain. Like a relay or train station, all information must first pass through your thalamus before being routed or directed to its destination in your brain’s cerebral cortex for further processing and interpretation.
relay station
The thalamus has many functions, including:
Relaying sensory information
Relaying motor (movement) information
Prioritizing attention
Role in consciousness
Role in thinking (cognition) and memory
-Taking in information, in the form of nerve signals, from all of your senses (taste, touch, hearing, seeing), except smell, into your brain. Each sensory function has a thalamic nucleus that receives, processes and transmits the information to its related area within your cerebral cortex.
Relaying sensory information
-Similar to sensory information, motor pathways all pass through your thalamus.
Relaying motor (movement) information.
-Your thalamus helps decide what to focus on among the vast amount of information that it receives.
Prioritizing attention.
-Your thalamus plays a role in keeping you awake and alert.
Role in consciousness.
-Your thalamus is connected with structures of your limbic system, which is involved in processing and regulating emotions, formation and storage of memories, sexual arousal and learning.
Role in thinking (cognition) and memory.
-is a small area in the center of the brain, located between the pituitary gland and the thalamus
hypothalamus
the hypothalamus is involved in the production and secretion of the following chemical messengers:
Antidiuretic hormone (ADH) or Vasopressin
Corticotropin-releasing hormone (CRH)
Gonadotropin-releasing hormone (GnRH)
Oxytocin
Thyrotropin-releasing hormone (TRH)
Somatostatin
Dopamine
-which helps maintain blood pressure and water volume.
Antidiuretic hormone (ADH) or Vasopressin
-which regulates metabolism and immune response. It is particularly responsive to stress.
Corticotropin-releasing hormone (CRH)
-which influences the release of sex-related hormones (FSH and LH)
Gonadotropin-releasing hormone (GnRH)
-This hormone aids in childbirth and breast milk production The hypothalamus produces oxytocin, that's stored and released by the posterior pituitary gland.
Oxytocin
-which regulates thyroid gland activity.
Thyrotropin-releasing hormone (TRH)
-Inhibits the release of growth hormone and thyroid-stimulating hormone
Somatostatin
-Known as the "feel-good" hormone, it affects mood and motivation
Dopamine
(also known as hypophysis) is a small, pea-sized gland located at the base of the brain below the hypothalamus. It sits in its own little chamber under the brain known as the sella turcica. It releases several important hormones and controls the function of many other endocrine system glands, hence it is often referred to as “master gland”
Pituitary gland
It sits in its own little chamber under the brain known as the _____________.
sella turcica
Your pituitary gland is divided into two main sections:
anterior pituitary (adenohypophysis)
posterior pituitary (neurohypophysis)
Your pituitary is connected to your hypothalamus through a stalk of blood vessels and nerves called the _______________ (also known as infundibulum)
pituitary stalk
The anterior lobe of your pituitary gland makes and releases the following hormones:
Adrenocorticotropic hormone (ACTH or corticotrophin)
Follicle-stimulating hormone (FSH)
Growth hormone (GH)
Luteinizing hormone (LH)
Prolactin
Thyroid-stimulating hormone (TSH)
-ACTH plays a role in how your body responds to stress. It stimulates your adrenal glands to produce cortisol (the “stress hormone”), which has many functions, including regulating metabolism, maintaining blood pressure, regulating blood glucose (blood sugar) levels and reducing inflammation, among others.
Adrenocorticotropic hormone (ACTH or corticotrophin)
-FSH stimulates sperm production in people assigned male at birth. FSH stimulates the ovaries to produce estrogen and plays a role in egg development in people assigned female at birth. This is known as a gonadotrophic hormone.
Follicle-stimulating hormone (FSH)
-In children, growth hormone stimulates growth. In other words, it helps children grow taller. In adults, growth hormone helps maintain healthy muscles and bones and impacts fat distribution. GH also impacts your metabolism (how your body turns the food you eat into energy).
Growth hormone (GH)
-LH stimulates ovulation in people assigned female at birth and testosterone production in people assigned male at birth. LH is also known as a gonadotrophic hormone because of the role it plays in controlling the function of the ovaries and testes, known as the gonads.
Luteinizing hormone (LH)
-stimulates breast milk production (lactation) after giving birth. It can affect fertility and sexual functions in adults.
Prolactin
- TSH stimulates your thyroid to produce thyroid hormones that manage your metabolism, energy levels and your nervous system.
Thyroid-stimulating hormone (TSH)
The posterior lobe of your pituitary gland stores and releases the following hormones, it is synthesized in the hypothalamus:
Antidiuretic hormone (ADH, or vasopressin)
Oxytocin
-This hormone regulates the water balance and sodium levels in your body.
Antidiuretic hormone (ADH, or vasopressin)
-Your hypothalamus makes oxytocin, and your pituitary gland stores and releases it. In people assigned female at birth, oxytocin helps labor to progress during childbirth by sending signals to their uterus to contract. It also causes breast milk to flow and influences the bonding between parent and baby. In people assigned male at birth, oxytocin plays a role in moving sperm.
Oxytocin
The small, cone-shaped pineal gland is located deep in the cerebral hemispheres and is attached to the thalamus near the upper part of the third ventricle. It secretes the hormone melatonin Melatonin functions as a biologic clock and can help to regulate the circadian rhythms, which are associated with environmental day and night cycles and help the body to distinguish day from night. Altered melatonin levels may result in variations of appetite, body temperature, and sleep pattern.
. It's often called the "third eye" due to its role in regulating light and dark cycles in the body.
Pineal Gland
-pineal gland secretes the hormone __________________
melatonin
Melatonin functions as a_________________ and can help to regulate the_________________, which are associated with environmental day and night cycles and help the body to distinguish day from night.
biologic clock
circadian rhythms
in pineal gland It's often called the _________________ due to its role in regulating light and dark cycles in the body.
"third eye"
-is a complex set of structures located deep within the brain. It plays a crucial role in regulating emotions, behavior, and memory.
limbic system
Here are some key components of the limbic system:
Amygdala
Hippocampus
Hypothalamus
Thalamus
Cingulate Gyrus
-Involved in emotion regulation, especially fear and pleasure.
Amygdala
-Essential for forming new memories and connecting emotions to those memories.
Hippocampus
-Regulates bodily functions such as hunger, thirst, sleep, and body temperature.
Hypothalamus
-Acts as a relay station for sensory information, directing it to the appropriate parts of the brain.
Thalamus
-Involved in emotional processing and regulation.
Cingulate Gyrus