Week 6 - Nervous System Chapter 12
The nervous system is divided into two subdivisions:
(CNS)Central Nervous System and the Peripheral Nervous System (PNS)
_______ _______ is divided into somatic nervous System (SNS), and autonomic nervous System (ANS)
Motor division
The Somatic nervous system
Supplies motor impulses to the skeletal muscles
The autonomic nervous system
- Supplies motor impulses to cardiac muscle, smooth muscle, and glandular epithelium.
- Regulates involuntary or automatic functions
This system is further subdivided to sympathetic & parasympathetic divisions
The autonomic nervous system
Consists of brain & spinal cord, encased in bone for protection.
CNS
Consists of nerves & ganglia.
- Further subdivided into an afferent (sensory) division & an efferent (motor) division
PNS
The ______ or sensory division is responsible for the transmission of impulses from the peripheral organs to the CNS
Afferent
The ________ or moter division is responsible for conveying neural signals from the central nervous System (CNS) to the peripheral organs, thereby eliciting a physiological response or action
Efferent
Functions of Nervous System
Helps keep the body balanced (homeostasis) by sensing changes, processing information, and responding.
Enteric Plexuses
Controls digestive functions
Nervous tissue is made of:
Neurons (nerve cells) and neuroglia (supporting cells).
Neurons have three main parts:
Dendrites: Receive signals, Cell Body: Processes signals, Axon: Sends signals to other cells.
________ are where neurons connect and communicate
Synapses
_______ terminals release chemicals called neurotransmitters.
Axon
Multipolar neurons
Many connections
Bipolar nuerons
Two connections
Pseudounipolar nuerons
One main connection.
Neurons are classified by function: Sensory Neurons
Bring information into the CNS.
Motor Neurons:
Send information out to muscles and glands.
Interneurons
Connect sensory and motor neurons within the CNS
________ protect and support neurons and help maintain the fluid around them.
Neuroglia
Types of neuroglia include:
In the CNS: Astrocytes, Oligodendrocytes, Microglial Cells, Ependymal Cells.
In the PNS: Schwann Cells, Satellite Cells.
Myelin Sheaths are:
Protective coverings for axons
_________ make myelin in the CNS.
Oligodendrocytes
_______ cells make myelin in the PNS.
Schwann
_____ Matter has myelinated axons, while _____ Matter contains neuron cell bodies and unmyelinated parts.
White, gray
Neurons and muscle fibers create electrical signals using four types of ion channels:
Leak channels
Ligand-gated channels
Mechanically gated channels
Voltage-gated channels
Neurons communicate using graded potentials for _____ distances and nerve impulses for _____ distances.
Short, long
A typical resting potential for a neuron is negative seventy millivolts. This means the cell is _____.
Polarized
The resting potential is influenced by:
Uneven distribution of ions inside and outside the cell.
Negative ions inside the cell that can’t leave.
Activity of sodium-potassium pumps.
In the _____, gray matter forms an inner core, surrounded by white matter.
Spinal cord
In the _____, a layer of gray matter covers the outer parts.
Brain
A ______ potential is a small change in the resting potential caused by the opening or closing of ion channels.
Graded
A _________ graded potential makes the inside of the cell more negative.
Hyperpolarizing
A ________ graded potential makes the inside of the cell less negative.
Depolarizing
The size of a graded potential varies based on how strong the ________ is.
Stimulus
Action potentials follow the _______ principle: if a stimulus is strong enough, it generates a constant-sized impulse
all-or-none
During an action potential, sodium and potassium channels open and close, causing ________
depolarization
There’s a _______ period where another action potential can’t be generated immediately.
refractory
Action potentials travel without getting _______, making them effective for long-distance communication.
Smaller
________ conduction is when impulses jump between gaps in the myelin sheath, making it faster than continuous conduction.
Saltatory
Larger/Smaller axons conduct impulses more quickly than smaller ones.
Larger
The strength of a stimulus is encoded in how often _______ occur and how many sensory neurons are activated.
Impulses
A _______ is where one neuron connects to another or to a muscle or gland. There are electrical and chemical synapses.
Synapse
In a _______ synapse, information flows in one direction, from the presynaptic neuron to the postsynaptic neuron.
Chemical
_______ neurotransmitters bring the postsynaptic neuron closer to generating an impulse, while ______ neurotransmitters make it less likely.
Excitatory, inhibitory
There are two main types of neurotransmitter receptors:
Ionotropic receptors: directly linked to ion channels.
Metabotropic receptors: linked to ion channels through G proteins.
Neurotransmitters are removed from the synapse by:
Diffusion
Enzymatic breakdown
Reuptake by cells
The ________ neuron recognizes signals and responds accordingly.
postsynaptic
Neurotransmitters are classified into two groups based on size:
Small-molecule neurotransmitters: like acetylcholine and amino acids.
Neuropeptides: made of three to forty amino acids.
The transmission of signals can be modified by changing the _____,_____,______ of neurotransmitters or affecting their receptors.
Synthesis, release, or removal
Neurons in the CNS are organized into networks called:
neural circuits
Types of neural circuits:
series, diverging, and converging circuits.
In the ______, axons can repair if the cell body is intact, Schwann cells are working, and scar tissue doesn’t form too quickly.
PNS
Neurogenesis
The creation of new neurons
The nervous system can change with experience (plasticity), but its ability to repair itself is _______.
limited