Animal Responses + Muscular contraction Flashcards
why and how do animals respond to their environment
- responding to internal and external stimuli increases their chance of survival
- receptors detect stimuli
- communicate with the nervous system and hormonal system
what is the central nervous system composed of
- brain
- spinal cord
what is the peripheral nervous system composed of
Somatic - conscious activities
Autonomic - unconscious activities
Sympathetic - body ready for action
Parasympathetic - calms body down
what are the parts of the brain
- cerebrum
- cerebellum
- hypothalamus
- pituitary gland
- medulla oblongata
what is the cerebrum
- controls voluntary actions
- vision, hearing, learning, thinking
- largest part of the brain
- divided into two halves - cerebral hemisphere
- thin highly folded outer layer - cerebral cortex
what is the cerebellum
- controls unconscious functions
- muscle coordination, posture, balance
- underneath cerebrum
- folded cortex
what is the medulla oblongata
- autonomic control
- heart rate and breathing rate
- base of the brain
- top of spinal cord
what is the hypothalamus
- regulatory centre
- temperature
- produces hormones to control pituitary
- beneath middle section
what is the pituitary gland
- stores and releases hormones
- stimulates glands
- releases hormones
- controlled by hypothalamus
- beneath hypothalamus
what is a reflex arc
- pathway of neurones in a reflex action
- receptor
- sensory neurone
- relay neurone
- motor neurone
what is the withdrawal reflex
- stimulus of heat
- thermoreceptor in skin detects heat
- sensory neurone passes nerve impulse to spinal cord
- relay neurone passes impulse across spinal cord
- motor neurone passes impulse to muscle
- effector contracts
- response - hand is moved quickly away from the flame
what is the knee- jerk reflex
- used to maintain posture and balance without little effort or though
- leg tapped at the patella (below kneecap)
- patellar tendon stretches and acts as a stimulus
- stimulus initiates a reflex arc causing extensor muscle in the thigh to contract
- relay neurone inhibits motor neurone of flexor muscle causing it to relax
- contraction coordinated with the relaxation of the antagonistic flexor hamstring muscle causing the leg to kick
what is the blinking reflex
- cranial reflex - occurs in the brain
- consensual response - both eyes close
- cornea is irritated
- stimulus triggers impulse along sensory neurone
- impulse passes through relay neurone in the lower brain stem
- impulse sent along motor neurone
- motor neurone closes eyelids
what is the importance of reflexes for survival
- involuntary response
- not having to be learnt
- extremely fast
what is skeletal muscle
- conscious control
- striated
- rapid contraction - speed and strength and fatigue quickly
- slow contraction - posture and endurance
- many nuclei
- long muscle fibres
- responsible for movements
what is cardiac muscle
- myogenic
- muscle fibres connected by intercalated discs that have low electrical resistance for easy impulse transmission
- branched - simultaneous contraction
- involuntary movement
- some cross- striations but not as strong
- contract rhythmically and don’t fatigue
- unnucleated
what is smooth involuntary muscle
- non-striated
- in walls of hollow internal organs - helps move food along the gut
- unnucleated
- spindle shaped fibres
- contract slowly and don’t fatigue
what is the structure of skeletal muscle
- muscle fibres
Muscle Fibres
- enclosed in plasma membrane - sarcolemma
- sarcoplasm - shared cytoplasm within a muscle fibre
- sarcolemma fold inwards to form T Tubules to spread electrical impulses throughput sarcoplasm
- sarcoplasmic reticulum
- lots of mitochondria to produce ATP
what is the structure of skeletal muscle
- Myofibrils
- long cylindrical organelles of proteins specialised for contraction
- Actin - thin filament
- myosin - thick filament
- alternating light and dark bands resulting in a striped appearance
Light bands - actin and myosin don’t overlap
Dark bands - thick myosin filaments, overlap with actin
Z-line - centre of each light band, contain sarcomere
H-Zone - light colour region in each dark band, myosin only
what is the sliding filament model
- myosin filaments pull actin filaments inwards towards the centre of the sarcomere
- light band becomes narrower
- Z line moves closer
- sarcomere shortens
- H zone becomes narrower
what is the structure of myosin
- globular hinged heads allowing them to move back and forth
- head has a binding site for actin and ATP
- tails of myosin molecules align to form myosin filaments
what is the structure of actin
- binding sites for myosin heads
- resting state the binding sites are blocked by tropomyosin held in place by troponin
- when stimulated the myosin heads form bonds with actin called actin-myosin cross bridges
what are the four stages of muscle contraction
- action potential triggers an influx of calcium ions
- ATP moves myosin head
- ATP breaks cross bridge
- Excitation stops
what happens when an action potential triggers an influx of calcium ions
- action potential stimulates muscle cell and depolarises sarcolemma
- depolarisation spreads down T-Tubules to sarcoplasmic reticulum
- reticulum releases calcium ions into sarcoplasm
- calcium ions binds to troponin causing it to change shape
- pulls tropomyosin out of the actin filament
- myosin head binds forming actin-myosin cross bridges
what happens when ATP moves the myosin head
- calcium ions activate ATPase to break ATP into ADP and Pi to provide energy
- energy moves myosin head which pulls actin filament along in a rowing action
what happens when ATP breaks the cross bridge
- myosin head detaches from the actin
- myosin head reattaches to another binding site further along the actin
- new actin-myosin bridge is formed and the cycle is repeated
- many cross bridges are formed and break rapidly pulling the actin along which shortens the sarcomere and the muscle contracts
- cycle continues as long as calcium ions are present and bound to troponin
Aerobic respiration
- ATP generated by oxidative phosphorylation in mitochondria
- long periods of low-intensity exercise
what happens when excitation stops
- calcium ions leave bindings sites on troponin
- calcium ions moved into sarcoplasmic reticulum by active transport
- troponin returns to their original shape pulling attached tropomyosin molecules
- tropomyosin blocks actin-myosin binding sites
- muscles aren’t contracted
- actin filaments slide back to relaxed position which lengthens the sarcomere
Anaerobic respiration
- ATP rapidly made by glycolysis
- end product is pyruvate which is converted to lactate by lactate fermentation
- lactate can quickly build up causing muscle fatigue
- good for short periods of hard exercise
ATP Creatine Phosphate system
- ATP made from phosphorylating ADP by adding a phosphate group from CP
- CP is stored inside cells
- ATP-CP system generates ATP quickly
- used for short bursts of vigorous activity
- anaerobic and a lactic
what are neuromuscular junctions
- synapse between motor neuone and muscle cell
- use ACh which binds to nicotinic cholinergic synapse
- release ACh depolarises post synaptic cell
- depolarisation of a muscle cell causes contraction
- acetylcholinesterase is stored in clefts on postsynaptic membrane is released to break down ACh after use
