Module 6: Functional Organizations of the Nervous Systems

What is the CNS made up of

brain and spinal cord

What does the brain do

receives and processes sensory info, initiates responses, sores memories and generates thoughts/emotions

What does the spinal cord do

conducts signals to and from brain; controls reflexes

What makes up the PNS

sensory and motor neurons

What do the motor neurons do

CNS to muscles and glands

What do the sensory neurons do

sensory organs to CNS

How is the motor division broken down further

somatic and autonomic

Somatic nervous system

controls voluntary movement

Autonomic Nervous System

controls involuntary responses

How is the autonomic broken down even further

sympathetic and parasympathetic

Sympathetic nervous system

fight/flight

Parasympathetic

Rest/Digest

What is the overview of organization

sensors

afferent neurons

integrating center

efferent neurons

effector organ

What do visceral sensory receptors monitor

internal conditions and the status of other organ systems

What are neurons organized into

neuronal pools

What do neuronal pools include

discharge zone and facilitated zone

What is the discharge zone

postsynaptic cells reach threshold

What is the facilitated zone

postsynaptic cells do not reach threshold but can easily from another stimulus source

How can input travel

along one or several different pathways

What is serial processing

input traveling along one pathway i.e. reflex

What is parallel processing

input traveling includes many pathways i.e. smelling a pickle

What is a diverging circuit

one input, many outputs

amplifying circut

What's an example of a diverging circuit

a single neuron in the brain can activate 100 or more motor neurons in the spinal cord and thousands of skeletal muscle fibers

What is a converging circuit

many inputs but one output

concentrating circuit

What is an example of converging circuit

different sensory stimuli can all elicit the same memory

What is a reverberating circuit

signal travels through a chain of neurons, each feeding back to previous neurons

oscillating circuit

controls rhythmic activity

Example of reverberating circuit

involved in breathing, sleep-wake cycle, and repetitive motor activities such as walking

What is a parallel after-discharge circuit

signal stimulates neurons arranged in parallel arrays that eventually converge on a single output cell

impulses reach output cell at different times, causing a burst of impulses called an after discharge

Example of parallel after-discharge circuit

May be involved in exacting mental processes such as mathematical calculations

What is the CNS of vertebrates encased in

bone or cartilage

What's the CNS of vertebrates surrounded by

meninges

What does the CNS of vertebrates float in

Cerebrospinal fluid

What separates the CNS of vertebrates from the rest of the body

blood brain barrier

What is gray matter

unmyelinated fibers and neuronal cell bodies

Where is gray matter in brain

superficial

Where is gray matter in spinal cord

deep

Where is white matter in brain

deep

Where is white matter in spinal cord

superficial

What are the three early embryo vesicles

forebrain, midbrain, hindbrain

What is another name for the forebrain

prosencephalon

What is another name for the midbrain

mesencephalon

What is another name for the hindbrain

rhombencephalon

What does the prosencephalon become

telencephalon and diencephalon

What does the midbrain become

mesencephalon

What does the hindbrain become

the metencephalon and myelencephalon

What does the telecephalon become

cerebrum

What does the diencephalon become

the thalamus and hypothalamus

What does the mesencephalon become

optic lobes (tectum) and midbrain nuclei

What does the metencephalon become?

cerebellum

pons

What does the myelencephalon become?

medulla oblongata

What makes up the hindbrain

medulla oblongata, pons, cerebellum

What does the medulla oblongata do

regulates breathing, HR, BP

What does the pons do

communicates info between medulla oblongata, cerebellum, and forebrain

What does the cerebellum do

integrates sensory info with motor commands

What does the midbrain do in mammals

serves as relay center

What does the midbrain do in fish/amphibians

serves as reflex center

What structure is found in the midbrain

optic lobes

What do the optic lobes do and what are they known as in mammals

-superior colliculi

-controls eye reflex and movements

What does the forebrain do

controls complex processes

What makes up the forebrain

cerebrum, thalamus, epithalamus, and hypothalamus

What does the corpus callsoum do

large grouping of commissural fibers that aid in communication between right and left hemisphere

What does the hypothalamus interact with

autonomic nervous system

What are the four F's of the hypothalamus

Fighting

Fleeing

Feeding

Fornicating

Where is the somatic sensory neuron located at in the spinal cord

dorsal root

What is the visceral sensory neuron located at in the spinal cord

dorsal horn

Where are interneurons in the spinal cord

dorsal horn

Where are the motor neurons in the spinal cord

ventral horn

Where is the somatic motor neuron located at in the spinal cord

ventral horn

Where is the visceral motor neuron located at in the spinal cord

ventral horn

What does the PNS consist of

somatic and autonomic divisions

What are the steps to the reflex arc

1. Arrival of stimulus and activation of receptor

2. Activation of a sensory neuron

3. Information processing in CNS

4. Activation of a motor neuron

5. Response by effector

What is the receptor

site of stimulus reception

What is a sensory neuron

afferent neuron

What is the integration center

can be monosynaptic or polysynaptic

What is a motor neuron

efferent neuron

What is an effector

cell that responds

What can reflexes be

somatic or visceral

What does stretched muscle do

activates the muscle spindle, increasing rate of APs

What does unstretched muscle do

APs are generated at constant raate in the associated sensory fiber

If only alpha motor neurons were activated

only the extrafusal muscle fibers contract. The muscle spindle becomes slack and no APs are fired. It is unable to signal further length changes

What is the normal coactivation of muscles

a and y

What happens if a and y activation occurs

both extrafusal and intrafusal muscle fibers contract. tension is maintained in the muscle spindle and it can still signal changes in length

Give the steps of tendon reflex

1. Quadriceps strongly contracts. Tendon organs are activated.

2. Afferent fibers synapse with interneurons in the spinal cord

3.a. efferent impulses to muscle with stretched tendon are damped. Muscle relaxes, reducing tension

3.b. efferent impulses to antagonist muscle cause it to contract

What does a noxious stimulus cause

flexor reflex on the same side, withdrawing that limb

What is the site of reciprocal activation

at the same time, the extensor muscles on the opposite side are activated

What is important to note about the autonomic nervous system

it is like a see saw, no regions are shut off but are balanced

What do effectors use

2-neuron chain

What are effector examples

smooth muscle, cardiac muscle, glands

Where does the preganglionic neuron have a cell body

CNS

Where does the postganglionic neuron have a cell body

in autonomic ganglion

What's is the difference between a ganglion and a basal nuclei

Ganglion are found outside the CNS, basal nuclei are found in the brain itself

What do all somatic motor neurons release

acetylcholine

What is the effect of somatic motor neurons

always excitatory

What do the ANS preganglionic fibers release

Acetylcholine

What do the ANS post ganglionic fibers release

acetylcholine or norepinephrine (adrenaline)

What can ANS pre/postganglionic effects be

either excitatory or inhibitory

What are the two cholinergic receptors

nicotinic and muscarinic

What are nicotinic receptors

can bind to nicotine; always excitatory

What does nicotinic receptors serve as

ion channel for Na+/Ca2+; all postganglionic fibers and somatic fibers

What can muscarinic receptors bind to

muscarine (fungal); can be excitatory/inhibitory