Unit III: Maintaining Homeostasis- chapter 9: Human Nervous system and homeostasis

Nervous system main purpose

to maintain and regulate a constant internal environment

sensory receptors

gather information from the external environment (skin, eyes, ear)

conducters

carry information (impulse transmission) from receptors to effectors or vice versa (neurons, nerves)

integrator

interpret and analyze sensory information and send information to effectors

effectors

part of the body that responds from an integrator (muscles, glands)

Central Nervous system

the brain and the spinal cord

Peripheral nervous system

the nerves that enter and leave the brain and spinal cord and service the various muscles, glands, and organs of the body

sensory neurons

take information from a receptor (such as pain or light) to CNS via interneurons

interneurons

connect sensory neurons to the CNS and the CNS to the motor neuron

motor neurons

receive information form the CNS (via interneurons) and carries it to an effector (muscles or gland)

Dendrite

branch like extensions that project out from the cell body and receives signals from other neurons

cell body

the main part if a neuron, filled with cytoplasm and containing the nucleus and other organelles. The control centre of the neuron

axon

long clindrical extension of a neuron's cell body that can range from 1mm to 1m in length. It transmists impulses along its length towards the next neuron

Schwann cells (including the myelin sheath)

special insulating cells around the axons of some nerve cells in the PNS

Schwann cells

make up of an outer layer called the myelin sheath (fatty layer around an axon). Myelin insulates the axon and speeds up nervous system

Node of Ranvier

the gap between Schwann cells around the axon of a nerve cell

Node of Ranvier

the membrane of the axon is exposed and nerve impulses jump from one node of Ranvier to the next for quick transmission

Axon terminal

the end of the axon that branches off and comes in close contact with the dendrites of neighboring neurons (does not touch them).

Dendrite

Axon

Node of ranvier

Axon terminal

Schwann cells (including myelin sheath)

Cell body

Nucleus

H

CNS and PNS where speed is needed

Where are myelinated neurons found?

The reflex arc

When a part of your body is stimuated, a nerve impluse is carried to your brain. Your brain sends an impulse to the stimulated area telling it what to do. This nerve pathway, from stimulus to reflex action is called the ______ ___ and involves three classes of neurons (nerve cells).

Reflex responses

involve all three types of neurons, but no brain involvement. They go through the spinal cord.

- chemicals

- light

- heat

- neurotransmitters

- pain

- smell

-taste

Neurons can be stimulated by:

mild stimulus, the threshold is not reached

if a neuron is given a _________________, there is a brief and small change in the charge of the cell membrne in the area of the stimulus but this does not continue down the length of the neuron ________________

the threshold of stimulus is reached or surpassed

however, a larger stimulus will cause the impulse to travel the length of the axon

All or none principle

if an axon is stimulated suffciently (above the threshold of stimulus), the axon will trigger an impulse down the length of the axon. if not, the impulse is not triggered.

1. uniform along the length of the axon

2. independent of the strength of the stimulus

once triggered the nervous response is:

-the number of neurons activated

- the typre of neurons activated (some neurons have higher thresholds than others)

strong environmental stimuli are determined by:

at rest

the outside of a neuron is positively charged compared to the inside.

at rest

sodium is pumped out of the cell by Na+/K+ pump

Resting potential

the difference in charge from the inside to the outside of a cell at rest

resting potential

approx -70 mV

Active transort

the sodium potassium pump is an example of:

Depolarization

Na+ gates open and Na+ rushes inside the axon

Depolarization

inside is now positively charged

Na+ gates and K+ gates are examples of:

passive transport

Repolarization

Na+ gates close

Repolarization

K+ gates open and K+ rushes out, making the inside more negative again.

Refractory period

the breif time between the triggering of an impulse along n axon and the axon readiness for the next impulse

0.001s

for many neurons the refractory period is about...

Synapase

junction (gap) between a neuron and another neuron or muscle cells

Neurotransmitters

chemicals that are secreted by neurons to stimulate motor neurons and CNS neurons

synaptic vesicles

specialzed vacuole in the bulb-like end of the axons of a nerve cell conatianing neurotransmitters that are released into the synapse when a nerve impulse is received

Excitory response

causes a wave of depolarization to occur in the next neuron

Inhibitory response

prevents depolarization (preventing nerve impluses) from occuring in the next neuron

Acetylcholine

Primary neurotransmitter of BOTH somatic NS and the parasympathetic NS

Acetylcholine

inhibits cardiac muscle (slows heart rate)

Cholinesterase

a neurotransmitter that breaks down Acetylcholine

Cholinesterase

causes skeletcal muscles to relax (inhibitory) and excites the cardiac muscle (excitatory - speeds up the heart rate)

Noradrenaline (norepinephrine)

readies the body to respond to danger or other stressful events

Noradrenaline (norepinephrine)

primary neurotransmitter of the sympathetic NS- exctitatory

Noradrenaline (norepinephrine)

over production linked to high blood pressure, anxiety, and insomia; deficiency linked to hunger cravings and exhaustion

Endorphins

act as natural pain killers in the brain; also affects emotional areas of the brain

Dopamine

neurotransmitter that elevates mood and controls skeletal muscle- excitatory

Seratonin

regulate temperature and sensory perception (alertness, sleepiness); is involved in mood

Dopamine

inadequate amounts in the brain synapses linked to depression

Brain is protected by

Meninges

bone

cerebral spinal fluid

Cerebrum

complex behaviours and intelligence; interpreting sensory inputs and initiating motor responses, speech, memory, and decision making, conscience and moral and ethical reassuring

Cerebellum

Responsible for muscle coordination and fine motor skills (ex. walking)

Cerebellum

allows you to "learn a skill over time" (get better with practice)

medulla oblongata

controls heart rates

medulla oblongata

adjusts blood pressure

medulla oblongata

controls breathing

medulla oblongata

controls vomiting

medulla oblongata

controls hiccupping

medulla oblongata

controls swallowing

medulla oblongata

damage to this region is FATAL

Midbrain

a short segment of the brainstem above the pons; particularly involved in sight and hearing

Pons

contains bundles of axons traveling between the cerebellum and the rest of the CNS

Pons

fucntions w/ the medulla oblongata to regulate breathing rate and reflex centers involved in head movement

Thalamus

sensory relay center of the brain

Thalamus

recieves mild sensations of touch, pain, hot, and cold

Hypothalamus

controls hunger, thirst, body temperature, anger, and aggression

Hypothalamus

Initiates immediate responses when the body is threatened (fight or flight)

Corpus callosum

connects left and right hemispheres of the brain

Corpus callosum

helps you concentrate and pay attention

Autonomic NS

relays information to the internal organs that are not under the conscious control of the individual

Autonomic NS

made up of the sympathetic and parasympathetic NS

Sympathetic NS

speeds up the muscle activity and activates in times of stress; "fight or flight response"

Parasympathetic NS

to slow down heart rate and relax muscles. Returns body to the "normal" state after a threat has passed

Parasympathetic NS

"rest and digest"

Somatic NS

relays info to and from skin and skeletal muscles that are mostly under the concious control of the individual

somatic NS, motor neurons, sensory neurons

in the ____________, ____________ connect muscles to the brain and _________ cary impulses to the brain from the snese organs

Somatic NS

some reflex movements can occur without a decision

Cerebrum

Thalamus

corpus callosum

Hypothalamus

pituitary gland

Midbrain

Pons

medulla oblongata

Cerebellum