Homeostatis 1

Parts of Nervous System

Central Nervous System(Brain, spinal cord) and peripheral nervous system(all other parts)

Peripheral - somatic(concious) and autonomic(not consious)

Somatic(voluntary) - sensory(relays info to cns) and motor(initiates response)

Autonomic(involuntary) - Sympathetic and parasympathetic

Dendrite function

Receive nerve impulse from other neurons or sensory receptors and transmit them to the cell body.

Cell body function

• contains nucleus and is site of metabolic processes

• processes input from dendrite and sends to axon if nerve impulse is large enough

Axon function

• conducts impulse away from cell body

Myelin sheath function

• protects neurons and speeds up the rate of nerve impulse transmission (saltatory conduction) by insulating axon

Motor neuron

• multipolar neuron

• transmits info from cns to effectors(muscles, glands etc)

Sensory neuron

• unipolar neuron

• sensory receptors receive stimuli and form nerve impulse and transit it to cns

Interneuron

• bipolar neuron

• connects sensory and motor neurons

where are types of neurons found

Bipolar - retinas, inner ear, olfactory area of brain
Multipolar - brain and spinal cord
Unipolar - peripheral nervous system

Reflex arc

1. receptor(pain) receives stimuli

2. sensory neuron then sends it to interneuron in spinal cord

3. sent to motor neuron which sends to effector

4. effector initiates response

Spinal cord

• carries nerve messages from receptors to brain

• communication link between pns and brain

• consists of grey and white matter

• protected by vertebral column and cerebrospinal fluid

Central Nervous System

• structural and functional centre for whole nervous system

• receives info from sensory neurons, processes info, and initiates response

• damage to cns can effect temperament, motor control, and homeostasis

White matter

• myelinated axons which make it white

• found in inner region of some parts of brain and outer area of spinal cord

Grey matter

• unmyelinated neurons

• grey because it consists of dendrites and cell bodies

• found in outside areas of brain and h shaped cone of spinal cord

regions of brain

• forebrain(thought, learning and emotion)

• midbrain(processing sensory input)

• hindbrain(coordination and homeostasis)

forebrain parts

• olfactory lobes, cerebrum, thalamus, hypothalamus, pituitary gland

• highly developed

midbrain parts

• 4 spheres of grey matter

• less developed

• relay center for some eye and ear reflexes

hindbrain parts

• joins with spinal cord

• cerebellum, pons, medulla oblongata

Label brain parts

What are meninges

• series of 3 membranes that surround and protect the central nervous system

Blood-brain barrier

• protective barrier formed by glial cells and blood vessels that seperates blood from cns

• selectively controls entrance of substances into the brain from the blood

Astrocyte

• type of glial cell that surrounds capillaries

cerebrospinal fluid

• clear dense liquid found in ventricles of brain and central canal of spinal cord

• transports hormones, wbc, and nutrients across blood-brain barrier to cells of brain and spinal cord

• cushions brain by acting as shock absorber

Cerebellum function

• unconsious coordination of posture, balance, body movements, reflexes, and fine, voluntary motor skills like writing, riding a bycycle

Medulla Oblongata function

• connects brain with spinal cord

• coordinates many reflexes and bodily functions like heart rate, rate of depth of breathing, swallowing, coughing

Pons function

• serves as relay center between neurons of the right and left halves of cerebrum, cerebellum, and rest of brain

Midbrain function

• process info from sensory neurons in eyes, ears, and more

• relays visual and auditory info between hindbrain and forebrain

• important for eye movement and control of skeletal muscles

Thalamus function

• contains neurons that provide connections between parts of brain (mainly between forebrain and hindbrain, areas of sensory system, and cerebellum)

• great relay station

Hypothalamus function

• helps regulate internal body environment and certain aspects of behaviour

• contains neurons that control bp, heart rate, body temp, and basic drives (fear, rage, pleasure)

Cerebrum function

• largest part of brain

• divided into left and right cerebral hemispheres

• intellect, learning and memory, conciousness, and language

• interprets and controls response to sensory info

Pituitary gland functions

• regulates growth, metabolism, and reproduction

What is cerebral cortex?

• thin outer covering of grey matter covering brain

• 5 mm thick and highly folded

• responsible for language, memory, personality, concious thought etc

What is corpus Callosum?

• bundle of white matter that connects 2 cerebral hemispheres of the cerebrum of brain

• sends messages from one cerebral hemisphere to other, telling it what the other half is doing

Occipital lobe function

• receive and analyze visual info

• recognizes what is being seen

Temporal lobe function

• also processes visual info

• auditory reception

• linked to understanding speech and verbal and visual memories

Parietal lobe function

• receives and processes sensory info from skin

• helps to process info about body’s position and orientation

Frontal lobe function

• integrate info from other parts of brain and control reasoning, critical thinking, personality, and memory

• contains motor areas that control various aspects of precise voluntary motor movement

function of somatic system

• control voluntary movement of skeletal muscles

• sensory neurons carry outside info inside

sensory neuron role in somatic system

• carry info about external environment inward, from receptors in skin, tendons, and skeletal muscles

motor neuron role in somatic system

• carry info to skeletal muscles

Cranial nerves

• 12 pairs

• largely associated with functions in head, neck and face

Spinal nerves

• contains sensory and motor neurons

• eg. thoriac nerves control muscles of rib cage

Autonomic system function

• controls involuntary glandular secretions and functions of smooth and cardiac muscle

• regulates bp, heart and breathing, digestion, body temp, metabolism, urination etc

• individual does not have to control body conciously

• controlled by hypothalamus and medulla oblongata

nerve role in autonomic system

• stimulate of inhibit glands or cardiac or smooth muscle

Sympathetic nervous system

• fight or flight response

• activated in stressful situations

• regulates voluntary processes in body

Parasymphathetic nervous system

• body is calm and at rest

• rest and digest response

• acts to restore and conserve energy

• regulates involuntary processes in body

Effector functions in symphathetic nervous system

• tear ducts inhibit tears

• pupils dilate

• salivary glands inhibit salivation

• lungs dilate air passageways

• increased heart rate

• liver stimulated to release glucose

• inhibits activity of pancreas, stomach, and kidneys

• adrenal glands stimulates adrenal secretion

• decrease of intestinal activity

• inhibits urination

Effector functions in parasymphathetic nervous system

• stimulates tears

• constricts pupils

• stimulates salivation

• constricts air passageways

• slows heart rate

• stimulates gallbladder to release bile

• increased activity of stomach and pancreas

• increases intestinal activity

• stimulates urination

What is homeostasis/dynamic equilibrium?

process by which a constant internal environment is maintained despite fluctuating external environment

body best working functions

• 37 degrees

• 0.01 blood sugar

• 7.35 pH

Homeostatic Control Systems

Monitors: special sensors found in organs

Coordinating/control center: relays info from monitors to necessary regulator

Regulator: helps restore balance(initiates action)

Negative Feedback

when a system deviates from norm, internal processes help to restore balance and normal conditions

Positive Feedback

• output enhances or turns up original stimulus

• helps amplify conditions away from norm

• eg. blood clotting

Thermoregulation

• mean body temp 36.8

• hypothermia <35

• temp regulation stops <30

• heatstroke >40

• endotherm can regulate temp, ectotherms can’t

Mammalian diving reflex

• heart rate slows

• hypothermia

• blood diverted to brain and other vital organs

Response to heat

1. sensors in hypothalamus detect change

2. nerve signal sent to sweat glands to start sweating

3. nerve signal also sent to blood vessels in skin to start dilating

Response to cold

1. sensors in hypothalamus detect change

2. nerve signal sent to skeletal muscles to start shivering

3. nerve signal sent to blood vessels in skin to start constricting

4. nerve signal sent to smooth muscles surrounding hair follicles to stand on end

Brown Fat Metabolism

• prolonged exposure to cold causes hormonal response that increases metabolism

• special adipose tissue efficient at producing heat when metabolized

• important in babies

Maintaining resting potential

• large negative protein molecules inside (cannot pass through membrane)

• K+ channels open more at resting potential so more K+ moves out then Na+ moves in

• Sodium Potassium pump transports Na+ and K+ in ratios keeping inside more negative

• more Na+ out of cell than K+ in cell

• creates electrochemical gradient

Sodium-Potassium Pump

• most important factor in maintaining resting membrane potential

• for every 3 Na+ ions pumped out, K+ pumped in

• necessary because Na+ and K+ ions slowly leak across membrane (K+ diffuses faster)

All or none response

• once -50 is reached, neurons fire maximally

• the more intense the stimulus, the greater the frequence of impulses

• intense stimuli excite more neurons (affects number of impulses reaching brain)

action potential steps

1. if it reaches threshold, Na+ voltage gated channels open and Na+ comes into cell, depolarizing it

2. Reaches 40 mV then Na+ channels are inactive and K+ voltage gated channels open

3. K+ leaves cell, repolarizing it and the charge drops to -90 mV, making it hyperpolarized

4. this is called refractory period where another action potential can’t occur

5. sodium-potassium pump works to bring it back to -70 mV

Synaptic Transmission steps

1. Action potential reaches axon end and depolarizes it

2. it causes Ca+ channels to open and Ca+ flows into presynaptic terminal

3. that causes the synaptic vesicles to fuse with presynaptic membrane

4. neurotransmitters exit through exocytosis into synaptic cleft and diffuse across it

5. binds to receptors on post synaptic neuron

6. if inhibatory, opens K+ channels and K+ diffuses out (no action potential, nerve signal stops)

7. if excitatory, opens Na+ channels and Na+ diffuses in ( action potential so nerve signal continues)

Neurotransmitters

• Acetylcholine acts as excitatory NT, opens Na+ channels, causing depolarization

• cholinesterase from post synaptic neuron destroys acetylcholine preventing constant state of depolarization

• inhibitory NT’s make post synaptic membrane more permeable to K+(more channels of Na+ need to be opened for action potential)

Summation

effect produced by accumulation of NT’s from 2 or more neurons