Animal Responses + Muscular contraction

Question 1

why and how do animals respond to their environment

Answer 1

• responding to internal and external stimuli increases their chance of survival
• receptors detect stimuli
• communicate with the nervous system and hormonal system

Question 2

what is the central nervous system composed of

Answer 2

• brain
• spinal cord

Question 3

what is the peripheral nervous system composed of

Answer 3

Somatic - conscious activities
Autonomic - unconscious activities

Sympathetic - body ready for action
Parasympathetic - calms body down

Question 4

what are the parts of the brain

Answer 4

• cerebrum
• cerebellum
• hypothalamus
• pituitary gland
• medulla oblongata

Question 5

what is the cerebrum

Answer 5

• 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

Question 6

what is the cerebellum

Answer 6

• controls unconscious functions
• muscle coordination, posture, balance
• underneath cerebrum
• folded cortex

Question 7

what is the medulla oblongata

Answer 7

• autonomic control
• heart rate and breathing rate
• base of the brain
• top of spinal cord

Question 8

what is the hypothalamus

Answer 8

• regulatory centre
• temperature
• produces hormones to control pituitary
• beneath middle section

Question 9

what is the pituitary gland

Answer 9

• stores and releases hormones
• stimulates glands
• releases hormones
• controlled by hypothalamus
• beneath hypothalamus

Question 10

what is a reflex arc

Answer 10

• pathway of neurones in a reflex action
• receptor
• sensory neurone
• relay neurone
• motor neurone

Question 11

what is the withdrawal reflex

Answer 11

• 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

Question 12

what is the knee- jerk reflex

Answer 12

• 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

Question 13

what is the blinking reflex

Answer 13

• 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

Question 14

what is the importance of reflexes for survival

Answer 14

• involuntary response
• not having to be learnt
• extremely fast

Question 15

what is skeletal muscle

Answer 15

• conscious control
• striated
• rapid contraction - speed and strength and fatigue quickly
• slow contraction - posture and endurance
• many nuclei
• long muscle fibres
• responsible for movements

Question 16

what is cardiac muscle

Answer 16

• 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

Question 17

what is smooth involuntary muscle

Answer 17

• non-striated
• in walls of hollow internal organs - helps move food along the gut
• unnucleated
• spindle shaped fibres
• contract slowly and don’t fatigue

Question 18

what is the structure of skeletal muscle
- muscle fibres

Answer 18

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

Question 19

what is the structure of skeletal muscle
- Myofibrils

Answer 19

• 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

Question 20

what is the sliding filament model

Answer 20

• 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

Question 21

what is the structure of myosin

Answer 21

• 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

Question 22

what is the structure of actin

Answer 22

• 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

Question 23

what are the four stages of muscle contraction

Answer 23

• action potential triggers an influx of calcium ions
• ATP moves myosin head
• ATP breaks cross bridge
• Excitation stops

Question 24

what happens when an action potential triggers an influx of calcium ions

Answer 24

• 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

Question 25

what happens when ATP moves the myosin head

Answer 25

- 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

Question 26

what happens when ATP breaks the cross bridge

Answer 26

- 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

Question 27

Aerobic respiration

Answer 27

- ATP generated by oxidative phosphorylation in mitochondria - long periods of low-intensity exercise

Question 27

what happens when excitation stops

Answer 27

- 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

Question 27

Anaerobic respiration

Answer 27

- 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

Question 28

ATP Creatine Phosphate system

Answer 28

- 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

Question 29

what are neuromuscular junctions

Answer 29

- 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