animal responses

• cerebrum

  receives sensory information

  sends out a motor impulse for a voluntary response -> conscious thought

  stores the memory of how to do an action
• cerebellum

  coordinates movement and balance

  learning a new skill
• medulla oblongata

  controls non-skeletal muscles

  autonomic center

  contains regulatory centers
• hypothalamus

  homeostatic center

  combines both nervous and endocrine systems
• pituitary gland

  regulated by the hypothalamus

  stores hormones
• central nervous system

  brain and spinal cord made up of white and grey matter
• peripheral nervous system

  made up of sensory and motor neurons
• autonomic

  non conscious thought
• somatic

  voluntary contraction of skeletal muscles
• parasympathetic

  relaxes the body
• sympathetic

  fight or flight response
• fight or flight response

  hypothalamus (nervous):

  activates the sympathetic nervous system

  impulses activate smooth muscle and glands

  and also activates the adrenal medulla to release adrenaline and noradrenaline into the bloodstream
• fight or flight response

  hypothalamus (endocrine):

  activates adrenal cortical system by releasing CRF

  this causes the pituitary gland to secrete the hormone ACTH

  which activates the adrenal cortex which releases hormones into the bloodstream
• cardiac muscle

  heart muscle is myogenic

  under autonomic control

  striated cells with intercalating discs

  lots of mitochondria

  uninucleated cells
• reflex arc

  receptors detect a stimulus -> sensory neuron -> relay neuron in the spinal cord -> motor neuron -> response brought about by an effector
• survival benefit of a reflex arc

  only 3 neurons involved

  not under conscious control
• knee jerk reflex

  tapping the patella tendon

  stimulates stretch mediated receptors

  impulse travels from a sensory to a motor neuron

  causes the muscles to contract
• name these tissues

  a -> striated skeletal muscle

  b -> involuntary smooth muscle

  c -> cardiac muscle
• skeletal muscle

  striated muscle

  attaches bones to muscles via non elastic tendons

  under somatic voluntary control

  muscle fibers contain lots of myofibrils

  multinucleated cells
• involuntary smooth muscle

  present in organ walls like the intestines

  under autonomic involuntary control

  no fibers or striations
• adrenaline and the secondary messenger model

  adrenaline released by the adrenal medulla is the first messenger that binds to complimentary receptors on target cells

  a hormone-receptor complex is formed which activates adenyl cyclase to convert ATP into cAMP

  cAMP then acts as a secondary messenger to initiate a cascade of enzyme activity within the cell

  example: activates Kinase which results in glycogenolysis
• myofibril structure

  z line -> boundary between sarcomeres

  I band -> only actin (appears lighter)

  a band -> overlap of actin and myosin

  h zone -> only myosin

  
• neuromuscular junction

  nervous impulse arrives at the neuromuscular junction

  voltage-gated Ca 2+ channels open

  this causes vesicles containing acetylcholine to fuse with the presynaptic membrane

  acetylcholine is released into the synaptic cleft and binds to receptors on the post synaptic membrane known as the sarcolemma

  Na+ ion channels open causing depolarisation of the sarcolemma and muscle contraction
• role of Ca 2+ in muscle contraction

  action potential carried through the sarcoplasm

  causes Ca 2+ channels to open in the sarcoplasmic reticulum

  Ca 2+ then binds to troponin

  causes a conformational change in tropomyosin

  exposing the binding sites on actin allowing actinmyosin bridges to form
• actin

  two thin strands twisted together
• myosin

  thick filaments

  heads at each end

  arranged in bundles
• sliding filament model

  Ca 2+ binds to troponin which causes a conformational change in tropomyosin exposing the myosin binding sites on actin

  myosin heads with ADP attached form cross bridges with actin

  the myosin heads then change shape and lose ADP pulling the actin along known as a power stroke

  ATP attaches to the myosin head causing it to detach

  the ATP is then hydrolysed by ATPase into ADP which re-attaches to the myosin head
• how does the sliding filament model show how the microfibril shortens

  the myosin heads pull the actin filaments towards each other

  distance between adjacent sarcomere z lines shorten
• role of creatine phosphate

  phosphorylates ADP into ATP when oxygen for aerobic respiration is limited
• baroreceptors

  location: carotid body

  detect changes in blood pressure
• chemoreceptors

  location: carotid body

  detects changes in blood ph
• response to an increase in blood pressure

  baroreceptors send more impulses to the cardioinhibitory center in the medulla oblongata

  more impulses to the SAN via the parasympathetic nervous system

  stimulates the release of acetylcholine which decreases heart rate
• response to a decrease in blood pressure

  baroreceptors send more impulses to the cardioacceleratory center in the medulla oblongata

  more impulses to the SAN via the sympathetic nervous system

  stimulates the release of noradrenaline

  which increases heart rate and strength of contraction
• increase in carbon dioxide concentration

  chemoreceptors detect ph decrease and send more impulses to the cardioacceleratory center of the medulla oblongata

  more impulses to the SAN via the sympathetic nervous system

  heart rate increases so rate of blood flow around the body inceases