animal transport

• central nervous system - brain and spinal cord, controls all body functions
• peripheral nervous system - sensory and motor neurones only
• autonomic nervous system - involuntary, homeostatic mechanisms
• sympathetic nervous system - fight or flight response, increases heart rate, blood pressure etc.
• somatic nervous system -

  • voluntary movements, conscious control over muscles
  • target tissue - skeletal muscle
  • excitatory effect
  • 1 neurone in pathway
  • myelinated neurones
• parasympathetic

  • sleep and relaxation
  • target tissue = cardiac and smooth muscle
  • excitatory or inhibitory effet
  • 2 neurones in pathway
• cerebrum - conscious thought and imagination
• cerebellum - controls muscle coordination, balance, and posture
• medulla oblongata - controls heart rate and blood pressure, and regulates breathing
• hypothalamus - controls body temperature, hunger, and homeostatic mechanisms
• pituitary gland - releases hormones produced by the hypothalamus
• reflex - a rapid and involuntary response to a stimulus
• reflex process

  1. stimulus detected by a receptor
  2. impulse travels along sensory neurone to the dorsal root ganglion
  3. either to a relay neurone or motor neurone
• reflexes such as the blinking reflex can be inhibited due to the presence of a synapse
• blinking reflex

  1. sensory neurone in the cornea sends an impulse to the brain stem
  2. synapses with a relay neurone
  3. a motor neurone then causes muscles to contract
  4. inhibitory neurone is myelinated
• fight or flight response

  1. stimulus detected by the hypothalamus which activates the sympathetic nervous system
  2. adrenaline is released from the adrenal medulla
  3. hypothalamus releases CRH and TRH which stimulate the pituitary gland
  4. pituitary gland releases ACTH which stimulates the production of cortisol
• control of heart rate - cardiac muscle requires oxygen and glucose and the removal of carbon dioxide
• if heart rate too slow

  1. cardio vascular centre detects and sympathetic/ accelerator nerve releases nordarenaline to speed up the impulses generated from the san
• if heart rate too fast

  detected in the cardiovascular centre in the medulla oblongata, parasympathetic/vagus nerve releases acetylcholine to decrease the heart rate
• nervous control of the heart - sensory neurones send messages to the cardiovascular centre

  • stretch receptors in muscles - detect movement
  • baroreceptors in carotid artery - detect pressure changes
  • chemoreceptors in the brain and aorta - detected changes in pH
• hormonal control of the heart

  the adrenal medulla secretes adrenaline and noradrenaline which bind to specific receptors in the san increasing the frequency and strengths of the heart beat
• voluntary/ skeletal muscle structure

  • striated
  • cylindrical cells
  • multinucleate
  • found in limbs and intercostal muscles
  • function - to move bones at joints
• involuntary/smooth muscle structure

  • non striated
  • spindle shaped
  • uninucleate
  • found in bronchioles, arteries, iris, intestine
  • function - control diameter of above, pupil size
• cardiac muscle

  • striated
  • branched with intercalated discs
  • uninucleate
  • found in the heart
  • function - to pump blood around the body and removal of waste products of respiration
• t tubules - infolding of the sarcolemma
• sarcolemma - cell surface membrane of the muscle fibre
• sarcoplasm - cytoplasm of the muscle fibre
• sarcoplasmic reticulum - stores calcium ions and releases it when muscle contracts
• events at a neuromuscular junction

  1. voltage gated calcium channels open and calcium ions diffuse in
  2. calcium ions cause vesicles to move and fuse with the presynaptic membrane releasing acetylcholine into the cleft
  3. acetylcholine binds to receptors on the sarcolemma
  4. sodium ions flood in causing the membrane to depolarise
  5. calcium channels open and calcium ions diffuse out of the sarcoplasmic reticulum
  6. calcium ions bind to proteins causing muscle contraction
• sarcomere - the region between two z lines
• h zone = just myosin

  decreases when muscles contract
• z line - holds thin actin filaments
• m line - holds thick myosin filaments
• I band - light

  decreases when muscle contracts
• a band - dark

  remains the same when muscle contracts
• myosin filaments

  • fibrous proteins
  • tail attached to m line
• actin filaments

  • two helical strands of globular proteins
  • coiled around fibrous tropomyosin
  • troponin molecules bind to the tropomyosin at intervals
• sliding filament model

  1. when relaxed there are no cross bridges and tropomyosin covers the actin binding sites
  2. calcium ions released by the sarcoplasmic reticulum bind to troponin causing the troponin to change shape and moving the tropomyosin, exposing the actin binding sites
  3. myosin heads bind to the actin forming cross - bridge
  4. myosin heads bend causing the thin filament to be pulled along so it overlaps - power stroke
  5. atp attaches to the myosin heads causing them to detach from the binding sites
  6. atp is hydrolysed causing the heads to move back to their previous position
• atp for muscle contraction

  • only enough atp stored in muscle for 1-2s
  • creatine phosophate is held in the sarcoplasm and used to create more atp
  • aerobic respiration supplies muscles with atp
  • glycogen reserves and oxygen from oxygen-myoglobin can be used
  • anaerobic respiration comes last as it leads to the build up of lactic acid
• electromyograph - an electrical signal can be sent across the fibres that make the muscle. the signal can be detected through electrodes