Topic #7 Fundamentals of the Nervous System

What are the three functions of the NS

1. Sensory input

2. Integrate

3. Motor output

What does “sensory input” do in the NS

It gathers sensory input from external and internal stimuli

What does the “integration” do in the NS

It processes and interpret aka integrate sensory input and react in each moment

What does the “motor input” do in the NS

It dictate response by activating effector organs (muscles or glands); response

Name the (2) basic divisions of the NS

1. CNS: Central nervous system

2. PNS: Peripheral nervous sytem

what does the CNS consist of

the brain & spinal cord

• integration & command center

• receives sensory signals

• interprets & issues motor responses based on many factors

what does the PNS consist of

nerves that extend from the CNS

• cranial nerves- carry signals to and from the brain

• spinal nerves- carry to and from the spinal cord

Name the (2) division of the PNS

1. Sensory (afferent) division

2. Motor (efferent) division

What does the sensory (afferent) division in the PNS do

sensory receptors send signals thru PNS nerve fibers into the CNS

What does the motor (efferent) division in the PNS do

CNS sends signals thru PNS nerve fibers to muscles & glands

Name the (2) division for motor (efferent) division in the PNS

1. Somatic nervous system

2. Autonomic nervous system

what is the somatic nervous system in the PNS

it serves all structures outside of ventral cavity (skin, skeletal muscle, bones)

what is the autonomic nervous system in the PNS

It serves viscera in the ventral cavity (digestive tract, lungs, heart, bladder, etc.)

what does the nervous system mainly consist of

nervous tissue; composed of specialized cells densely packed & intertwined

what (2) things that the nervous tissue is made up of

1. neurons

2. neuroglia

what are neurons

they’re excitable nerve cells that transmit electrical signals

what are neuroglia

they’re nonexcitable support cells that surround & wrap the neurons

name the term that “transmits electrical signals along the plasma membrane”

neurilemma aka processes

how does the neurilemma transmit signals in the neuron structure

by their arm like extensions

what are the two processes of a neuron

1. axon

2. dendrites

what are “dendrites” in the neuron

short extensions that connect to other nearby neurons ; theres usually several dendrites in the neuron

what are the “axons” in the neuron

theres a single axon; it is a long extension that connects to distant neurons or other body structures

What are synapses

sites at which neurons communicate

how does synapses transmit info

synapses transmit info through chemical messaging via neurotransmitters because the synaptic signaling is unidirectional so it will determine the direction of info flow thru the nervous system

what does the synapses consists of

a terminal bouton from a neuron sending a signal full of synaptic vesicles that contain neurotransmitters

what does the terminal boutons form

the terminal boutons rest slightly apart from the membrane of a signal receiving cell to form a synaptic cleft

where are the neurotransmitters secreted into

the synaptic cleft; to bind to receptors that cause a new electrical signal

what are the neurons classified by

their structure and by the function

How are the neurons are grouped by STRUCTURALLY

they are grouped structurally according to the # of processes that extend from the cell body

How are the neurons are grouped by FUNCTIONALLY

they are grouped functionally according to the direction their signals travel relative to the CNS

what are the (3) classification of neurons

1. multipolar

2. bipolar

3. unipolar

what is a multipolar neuron

• they have more than 2 processes

• many dendrites & 1 axon

• 99% of neurons

what is a bipolar neuron

• have 2 processes

• extending from opposite ends of cell body

• occur in special sensory

what is a unipolar neuron

• short, single process

• extends from cell body that splits like a “T” into 2 branches

• sensory neurons in the PNS

All neurons associate closely with supporting cells that are called what

neuroglia aka glial cells

what are the (4) neuroglia in the CNS

1. Astrocytes

2. Microglial cells

3. Ependymal cells

4. Oligodendrocytes

what are the (2) neuroglia cells in the PNS

1. Satellite cells

2. Schwann cells

What are the characteristics of astrocytes

• they are star shaped cells abundant in the CNS

• many radiating processes attached to neurons & blood vessels

• help regulate neural signaling & blood flow thru nervous tissue

What are the characteristics of microglial cells

• small & least abundant

• they have macrophages

• able to migrate to and engulf invading microorganisms & injured or dead neurons

What are the characteristics of ependymal cells

• they form simple epithelium lining central cavity of the spinal cord & brain

• provides permeable layer b/w CNS cells & CSF filled cavities

• have cilia that help circulate CSF

What are the characteristics of oligodendrocytes

• large, flat cells processes that wrap around clustered axons in the CNS

• Wrapping insulates axons & helps them transmit signals faster

what do the satellite cells surround

neuron cells bodies within ganglia

what do the schwann cells surround

the axons in the PNS, forming myelin sheaths

what are myelin sheaths

they are segmented structures composed of a lipoprotein called myelin

what are myelinated sheaths

thick, rapidly conducting axons in the PNS; wrapped multiple times by a schwann cell

what are the unmyelinated sheaths

thin, slowly conducting axons in the PNS; they tend to be bundled together by schwann cells wrapped once over the axons

The CNS has two tissue types that are called

gray matter & white matter

The PNS is essentially a vast organization of ___ and ___

ganglia & nerves

what are the gray matter composed of

• neuron cell bodies

• neuron processes

• glial cells

• neuron to neuron synapses

the DORAL half in the gray matter contains what

cell bodies of interneurons

the VENTRAL half of the gray matter contains what

cell bodies of motor neurons

the neuron axons in the gray matter are unmyelinated or myelinated

unmyelinated

what does the white matter consists of

• no neuron cell bodies

• consists of just axons and glial cells

axons in the white matter are myelinated or unmyelinated

myelinated because of the extra fat content from the myelin sheaths

Most of the axons in the WHITE matter ascend from what

spinal cord to brain OR brain to spinal cord to facilitate communication

what are nerves

they are cable-like organs in the PNS

What does the nerves consist of

parellel axon bundles organized by layers of CT & blood vessels to nourish cells

Nerves are organized similarly to ___ muscle

skeletal

the OUTER perimeter that is covered in the CT is called ___

epineurium

within the epineurium are several distinct bundles of axons are called ___

fascicles

each fascicle is wrapped in a layer of CT is called ___

perineurium

within each fascicle are many parallel running are called the ____ axons

myelinated

each axon in fascicles are additionally wrapped in a delicate layer of CT is called the ___

endoneurium

the PNS is composed of nerves that contain both ___ and ___ axons

sensory (afferent); motor (efferent) axons

the CNS features interneurons that do what (3) things

1. receive sensory info

2. direct info to specific regions of the CNS

3. initiate appropriate motor responses

the structural link b/w PNS and CNS are called what

neuronal integration

the neuronal integration occur in what matter

gray matter

example of neuronal integration is the ..

reflex arc

what is the reflex arc

simple neuron chains that cause our simplest reflexive behaviors

reflex arcs accounts for ___: rapid, automatic motor responses to stimuli

reflexes

what is the SIMPLEST reflexes

monosynaptic

which reflex has one or more interneurons that are part of the reflex pathway

polysynaptic

Term for “networks can be very complex, allowing for the total behavioral and processing abilities of the NS”

Interneuron