PATHO Ch. 15 Structure and Function of the Neurologic System

The two main divisions of the nervous system are

central nervous system (CNS)

peripheral nervous system (PNS)

Central Nervous System (CNS)

brain and spinal cord

KEEPS US ALIVE

Peripheral Nervous System (PNS)

spinal and cranial nerves

PNS: afferent

carry information toward the CNS

PNS: efferent

carry information away from the CNS

somatic nervous system

part of the PNS

controls:

- skeletal muscles

- somatosensory (touch)

autonomic nervous system

part of the PNS

controls:

- glands + muscles of the internal organs (heart)

- automatic

sympathetic division arouses

parasympathetic division calms.

sympathetic nervous system

fight or flight

parasympathetic nervous system

rest and digest

homeostasis

The neurotransmitter released by preganglionic parasympathetic fibers is:

acetylcholine

vestibular

balance

auditory

hearing

olfaction

smell

gustatory

taste

neurons

nerve cell

primary communicating cell

specialized

polarized (axons: send, dendrites: receive)

different shapes and types

pseudounipolar neurons

have only one fused axon that extends from cell body and divides into TWO processes:

- one process carries sensory information FROM sensory receptors TO cell body;

- other process carries sensory information FROM cell body TO spinal cord;

bipolar neurons

A neuron that has only two projections (one axon/one dendrite) from the cell body

found in: retina

multipolar neuron

a nerve cell that has many dendrites and a single axon

- most common body neuron

every neuron in our body has only ONE

axon

we do NOT have _____ neurons in our body

true unipolar neurons

axon

A long, tail-like part that sends signals to other neurons, muscles, or glands

axon hillock (trigger zone)

acts like a trigger point that decides whether or not to send an electrical signal (action potential) down the axon.

cell body

contains nucleus and organelles

dendrites

Branch-like structures that receive signals from other neurons.

axon terminals

messenger stations that deliver signals to the next cell

schwann cell

wrap around axons of neurons and form a protective coating called the myelin sheath.

myelin

insulate the axon and help electrical signals travel faster and more efficiently along the nerve cells.

made by: shwann cells and oligodendrocytes

actin filaments

thin, thread-like protein fibers that are part of the cytoskeleton inside cells

intermediate filaments

strong, rope-like protein fibers that are part of the cytoskeleton inside cells.

microtubules

Spiral strands of protein molecules that form a tube-like structure

Which information is correct regarding interneurons? Interneurons:

transmit impulses between neurons in the same part of the nervous system

glia are in the ______ and _______

CNS + PNS

CNS glia

astrocytes, oligodendrocytes, microglia, ependymal cells

astrocytes

Provide structural and metabolic support for neurons.

form blood brain barrier

macroglia (bigger cells)

astrocyte end feet

cover capillaries and help control what substances can pass from the blood into the brain, keeping out harmful molecules.

if they didn't, body would attack our own neurons.

oligodendrocytes

Form myelin sheath in CNS

macroglia (bigger cells)

microglia

phagocytes

ependymal cells

lines ventricles + produce cerebrospinal fluid

PNS glia

Schwann cells and satellite cells

satelite cells

surround neuron cell bodies for support and fluid exchange

can form new neurons

they act like nurses

node of ranvier

small gap between the myelin sheath segments that cover an axon. These gaps are not insulated and are rich in ion channels.

Wallerian degeneration

degeneration of the distal portion of the axon and myelin sheath

distal changes

distal axon degrades

schwann cells induced to proliferate

proximal changes

sprouting (trying to recover by regenerating its axon)

regeneration of axons

ONLY in PNS

ONLY if lesion is small

if damage is close to cell body, more likely it is to die

nerve impulse (neurocommunication)

involves changes from the resting membrane potential (electrical) followed by release of a neurotransmitter that binds to receptors on target cell. target cell response depends on the neurotransmitter that is released.

two types of changes in nerve impulses

local change

generation of action potential

action potential

a neural impulse; a brief electrical charge that travels down an axon

nerve impulse: resting stage

"polarization"

the neuron is at rest with a negative charge inside and a positive charge outside

nerve impulse: triggering the impulse

"depolarization"

When a neuron gets stimulated (by a chemical signal, for example), sodium channels open.

Na⁺ ions rush in, making the inside more positive.

This change in charge creates an action potential (the actual nerve impulse).

nerve impulse: resetting the neuron

"repolarization"

To return to its resting state, potassium channels open and K⁺ ions flow out, making the inside negative again.

The sodium-potassium pump restores the original balance of ions.

nerve impulse: passing the message

"synaptic transmission"

When the impulse reaches the axon terminals, it triggers the release of neurotransmitters into the synapse (the gap between neurons).

Neurotransmitters bind to receptors on the next neuron, triggering a new impulse if the signal is strong enough.

postsynaptic neuron

neuron that receives the signal

presynaptic neuron

conducts impulses toward the synapse

temporal summation

process in which multiple nerve impulses from the same presynaptic neuron are sent one after another in quick succession to a single postsynaptic neuron. These rapid signals add up (or summate) over time to reach the threshold needed to trigger an action potential in the postsynaptic neuron.

spatial summation

multiple presynaptic neurons send signals at the same time to a single postsynaptic neuron. These signals add up (or summate) across different locations on the postsynaptic membrane. If the combined effect is strong enough to reach the threshold, it triggers an action potential (nerve impulse) in the postsynaptic neuron.

excitatory neurotransmitters

chemical messengers that increase the likelihood that a nerve impulse (or action potential) will be triggered in the postsynaptic neuron.

They do this by binding to receptors on the postsynaptic cell and causing positive ions (like sodium, Na⁺) to flow in, making the inside of the neuron more positive (a process called depolarization)

inhibitory neurotransmitters

decrease the likelihood that a nerve impulse (or action potential) will be triggered in the postsynaptic neuron.

They do this by binding to receptors on the postsynaptic cell and causing negative ions (like chloride, Cl⁻) to flow in or positive ions (like potassium, K⁺) to flow out.

This makes the inside of the neuron more negative (a process called hyperpolarization), moving it farther from the threshold needed to fire an action potential.

synapses

chemical

tiny gap between two neurons (or between a neuron and another cell, like a muscle cell) where nerve signals are passed from one cell to the next.

convergent signaling

when multiple neurons send signals to one single neuron

divergent signaling

one presynaptic neuron signals to multiple post-synaptic neurons

neurotransmitters

chemical messengers that carry signals between neurons by crossing the synapse (the gap between neurons). They can either excite or inhibit the next neuron, helping control everything from muscle movements to mood and memory.

common types of neurotransmitters

Monoamines - serotonin

Nucleotides/nucleosides - adenosine

Amino acids

Acetylcholine - in neuromuscular junctions

Neuropeptides

neuromodulation

activate receptor that is not an ion channel

3 major divisions of the brain

forebrain, midbrain, hindbrain

forebrain

telencephalon and diencephalon

telencephalon

cerebral hemispheres

diencephalon

thalamus and thalamus named structures

midbrain

the mesencephalon; the central of the three major divisions of the brain

hindbrain

medulla, pons, cerebellum

back of the brain

metencephalon + myelencephalon

Metencephalon

pons and cerebellum

myelencephalon

medulla

nuclei

clusters of cell bodies in the CNS (gray matter)

fibers/tracts

axon bundles in CNS (white matter)

it is white due to myelin from axons

function of cerebral hemisphere

sensory motor processing

- info coming from senses and how we form an action

5 lobes of the cerebrum

frontal, parietal, temporal, occipital, insula

sensory input leads to

motor response

frontal lobe

The lobe at the front of the brain associated with movement, speech, and impulsive behavior.

the frontal lobe contains

Prefrontal cortex

Premotor/supplementary motor cortex

Primary motor cortex

Broca's area

broca's area

speech production

You know that the premotor area (Brodmann area 6) is

involved in programming motor movements.

parietal lobe

A region of the cerebral cortex whose functions include processing information about touch.

- problem solving

- Wernicke area

Wernicke's area

language comprehension

occipital lobe

visual processing

temporal lobe

hearing

second vision area

olfactory (smell)

insular lobe

emotions, perception, self-awareness, and bodily sensations like pain, temperature, and taste. It also helps with empathy, decision-making.

limbic system

involved in emotions, memory, motivation, and behavior. It connects the higher-thinking parts of the brain with the emotional and survival-related areas.

hippocampus

memory

amygdala

fear and aggression

cingulate gyrus

plays role in expressing emotions via gestures and resolves mental conflict

diencephalon contains

thalamus, hypothalamus, epithalamus, subthalamus

thalamus

the brain's sensory control center, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla

epithalamus

Contains pineal body. Involved in olfactory senses and sleep/wake cycle

hypothalamus

brain region controlling the pituitary gland

hormones

subthalamus

works with basal ganglia for motor control

Mesencephalon contains

tectum and tegmentum

cerebral peduncles and aqueduct

mesencephalon function

vision, hearing, movement, and reflexes

pons

relays signals, controls breathing, aids in movement, regulates sleep

cerebellum

the "little brain" at the rear of the brainstem; functions include processing sensory input and coordinating movement output and balance

spinal cord

white matter is on the outside

gray matter on the inside