C13 - Neurones (pt2) - The nervous system

M5 - communication and energy

CNS - central nervous system

sensory information passes through the CNS to effect a motor response

• involves the brain (voluntary/involuntary responses)

• and the spinal chord (relax axons)

PNS - peripheral nervous system

involves all neutrons outside the brain and spinal chord

• somatic division and autonomic division

somatic nervous system

controls voluntary movement using effectors (e.g. skeletal muscle)

• under concious control

autonomic nervous system

under subconcious control, for involuntary movements - constantly working

• e.g. heart beat

• divided into sympathetic and parasympathetic

autonomic nervous system - parasympathetic

if the outcome decrease activity

• e.g. HR decrease after exercise

• often results in opposite effects on the body

• rest and digest

autonomic nervous system - sympathetic

increases activity

• e.g. Inc. in HR

• fight or flight

ganglia

a group of neurones

nerves

groups of axons

nuclei - in CNS

groups of neurons

tracts - CNS

groups of axons

structure of the brain

• cerebrum

• 4 lobes - frontal, temporal, occipital, parietal

• cerebellum

• medulla oblongata

• hypothalamus

• pituitary gland

structure of the brain - cerebrum

processes and controls most conscious thoughts and voluntary actions ( memory, learning)

• makes up most of the brain

• 2 hemispheres - left and right

• corpus callosum - connects hemisphere

• highly convoluted = inc. SA and complex activity

• protected by cerebral cortex

• 4 lobes

corpus callosum

connects the 2 hemisphere of the cerebrum

cerebral cortex

the outer layer of the cerebral hemispheres

• 2-4mm thick

cerebrum - frontal lobe

emotion, reasoning, problem solving and planning

• at the front of the brain (forehead area)

cerebrum - temporal lobe

sensory processing of hearing, memory and language formation, some visual processing (facial recognition)

• at bottom of brain - under frontal and parietal

cerebrum - occipital lobe

visual processing

• at back bottom of brain - behind temporal

cerebrum - parietal lobe

integrating sensory information (touch, pain, pressure)

• at back top of brain - behind frontal, above occipital

cerebellum

coordinated balance, movement and posture (unconscious functions and non-voluntary movement)

• responsible for fine motor control

• at bottom of brain - below temporal lobe/ cerebrum

• if damaged - may be jerky and uncoordinated

medulla oblongata

autonomic control - HR and BR, also coughing and swallowing

• connects spinal cord to higher brain regions

• infront of cerebellum - thick chord at base of brain

hypothalamus

regulatory centre for temp and water balance

• 2 centres - 1 parasympathetic, 1 sympathetic

• controls complex behaviour patterns

• monitors blood plasma composition

• produces hormones - like ADH

• found near medulla oblongata, above pituitary gland

pituitary gland

stores and releases hormones that regulate body functions

• anterior (front) and posterior (back) pituitary

anterior pituitary gland

produces 6 hormones

• including FSH - involved in reproduction and growth

posterior pituitary

stores and releases hormones produced nay hypothalamus

• e.g. ADH - involved in urine production

reflexes

a quick and automatic response to a stimulus

• information not processes in the brain, no decision is made

reflex arc

the pathway of neurones involved in reflex response

reflect arc - steps

• receptors = detect a stimulus

• sensory neuron = carries impulse from receptors to relay neuron (in spinal chord)

• relay neuron = carries impulse to motor neurone

• motor neurone = caries impulse to effectors

• effectors = brings about a response

spinal cord

column of nervous tissue running up the back

• surrounded by spine for protection

knee jerk relex

• spinal reflex = doesn’t involve the brain

• often tested by doctors

• leg tapped below patella - stretches pattelar tendon - acts as stimulus

• initiates reflex arc - extensor muscle on thigh contracts, relay neurone inhibits motor neurone of flexor muscle

• flexor muscle relaxes

• causes a leg kick

• absence of reflex = nervous problems

• multiple kicks = cerebellar disease

blinking reflex

exists to protect cornea from damage by dust or foreign objects - cranial reflex (only occurs in brain)

• cornea stimulated by touch = corneal reflex

• bright light blinking = optical reflex

• also occurs for loud sounds

blinking reflex - arc

• cornea irritated

• triggers impulse along sensory neurone (5th cranial nerve)

• passes through relay neurone

• sent to motor neurone (7th cranial nerve)

• initiate motor resposne to close eyes

• consensual response = both else close

• tested in unconscious patients

• liking functioning = lower brain stem functioning

survival importance of reflexes

• involuntary - brain isn’t overloaded

• not learned - provide immediate protection at birth

• fast - short relax arc

• form everyday actions - posture and digestion

types of muscle cell

cardiac, skeletal, involuntary

cardiac muscle

found only in the heart - keep heart beating consistently

• involuntary muscles

• single nucleated, branched, striated

• intermediate speed and length of contraction

• branches interconnect - simultaneous contraction

involuntary muscle

in blood vessels, bronchioles and organs, responsible for moving substances through body

• involuntary

• singly nucleated, not striated or branched

• slow and long contraction

• e.g. digetsive system

skeletal muscle

control limb movement, facial expression, swallowing and eye movement

• common

• voluntary

• multinucleated, striated, unbranched

• regular arrangement = one direction of contraction

• quick and short contraction

skeletal muscle - fibres

made up of many bundles of muscle fibres

• long specialised cells

skeletal muscle - sarcolemma

the membrane of an individual muscle fibre

• fold inwards to the sarcoplasm at some points

• T tubules = transverse inwards folds

• contain mitochondria - provide ATP for contraction

sarcoplasm

the cytoplasm in a muscle fibre

sarcoplasmic reticulum

an organelle in the sarcoplasm

• stores Ca2+ ions - needed for muscle contraction

myofibrils

cylindrical organelles that run along the length of muscle fibres

• the site of muscle contraction

• contain sarcomere, myofilaments, myosin filaments and actin filaments

sarcomere

units that run end to end along the myofibril

• make up myofibrils

• z line = end of a sarcomere

z line

end of a sarcomere

(unit that makes up myofibril)

myofilaments

2 myofilaments make up sarcomeres

• slide past eachother to allow contraction

• myosin = thick

• actin = thin

myosin myofilament

arranged in alternating pattern in sarcomere with actin

• thick

• overlaps thin actin - A band

• only myosin region - H zone

A band

overlapping region between actin and myosin filaments in sarcomere

h zone

the region with only thick myosin filament in the sarcomere

actin filament

• only overlaps myosin in middle of sarcomere - m line

• thin

• only actin region = I band

I - band

the region with only thin actin filament in the sarcomere

M line

the reigon at the middle of the sarcomere where actin overlaps myosin