Module 5.1.5- Animal responses

• Peripheral Nervous System (PNS)


  the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.
• Central Nervous System (CNS)


  consists of the brain and spinal cord
• Somatic Nervous System (SNS)


  this system is under

  conscious control

  and the part of the peripheral nervous system that controls voluntary movement of skeletal muscles
• Autonomic Nervous System (ANS)


  this system works constantly and is under subconscious control. it is involuntary
• The autonomic nervous system is further divided into the...


  sympathetic nervous system and

  parasympathetic nervous system
• Sympathetic nervous system


  a set of nerves that prepares the body for action in challenging or threatening situations increasing activity 'fight or flight' responses noradrenaline neurotransmitter

  
• Parasympathetic nervous system


  a set of nerves that helps the body return to a normal resting state decreasing activity relaxing responses acetylcholine neurotransmitter
• Summary of nervous system


  See diagram

  
• The brain is protected by the ________ and is surrounded by protective membranes called __________

  skull, meninges
• Brain structure- cerebrum


  responsible for coordinating the body's voluntary responses highly convoluted so high in surface area to increase its capacity for complex activity split into 2 hemispheres and left hemisphere controls right side of the body (and vice versa)

  
• Brain structure- cerebellum


  controls unconscious functions

  such as posture, balance and non voluntary movement coordinating it

  
• Brain structure- medulla oblongata


  used in autonomic control controls reflex activities such as breathing rate and heart rate. also controls activities such as swallowing, coughing etc.

  
• Brain structure- hypothalamus


  main controlling region for the autonomic nervous system has 2 centres-sympathetic and parasympathetic regulatory centre for temperature and water balance produces hormones (endocrine gland)

  
• Brain structure- pituitary gland


  split into 2:

  anterior pituitary- produces 6 hormones including FSH

  posteriori pituitary- stores and releases hormones produced by the hypothalamus such as ADH

  
• Reflex action


  An immediate response to a specific stimulus without conscious control.
• Reflex arc (touching a hot stimulus)

  - 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

  - hand is moved away

  
• Spinal cord


  column of nervous tissues running up from the back

  surrounded by spine for protection
• Knee-jerk reflex

  a variant of the stretch reflex in which stretching of the tendon beneath the knee leads to an upward kick of the leg

  spinal reflex -> neural circuit to spinal cord only (not brain)

  -when leg is tapped

  -patellar tendon is stretched and acts as a stimulus

  -the stimulus initiates a reflex arc that cause extensor muscle to contract- (simultaneously) a relay neurone inhibits the motor neurone of the flexor muscle

  Absence of this reflex may indicate nervous problems

  Reflex is used by the body to help maintain posture and balance

  
• Blinking reflex


  When the cornea of the eye is irritated by a foreign body

  the stimulus triggers an impulse along a sensory neurone the impulse then passes through a relay neurone in the lower brain stem impulses are then sent along branches of the motor neurone to initiate a motor response to close the eyelids.

  
• Cranial nerve (eye)


  occurs in the brain(not spinal cord) testing the corneal reflex
• Structure of an eye

  
• Survival importance

  - doesn't involve decision making so brain isn't overloaded (involuntary)

  -doesn't need to be learnt offering immediate protection

  - extremely fast

  -controls everyday actions, e.g. digestion
• Skeletal muscle


  -make up bulk the bulk of body muscle tissue

  -they are responsible for movement e.g. biceps

  -voluntary

  -rapid and short contractions

  -regularly arranged->allows for one direction muscle contraction-striated

  
• Cardiac muscle


  -found only in the heart

  -involuntary

  -intermediate speed and contractions

  -cells branch -> simultaneous contraction - specialised striated

  
• Smooth (Involuntary) muscle


  -found in many areas such as stomach and bladder

  -involuntary

  -slow and can have long contractions

  -no regular arrangement -> different cells contract in different contractions - non-striated

  
• Structure of skeletal muscle-


  muscle fibres made up of muscle fibres that are enclosed within a plasma membrane known as the sarcolemma

  -contain a number of nuclei and are longer than normal cells -> for strength

  -lots of mitochondria for ATP

  -modified ER (sarcoplasmic reticulum)

  ->contains Ca2+ ions for muscle contraction

  -parts of the sarcolemma fold inwards(increases SA) to help spread electrical impulses ->simultaneous contraction

  -cytoplasm is called sarcoplasm

  
• The muscle's cell surface membrane is called the _________ and the cytoplasm in the muscle is called the _________. It also contains a modified endoplasmic reticulum that releases Ca2+ ions for muscle contraction called the ___________.

  The muscle's cell surface membrane is called the sarcolemma and the cytoplasm in the muscle is called the sarcoplasm. It also contains a modified endoplasmic reticulum that releases Ca2+ ions for muscle contraction called the sarcoplasmic reticulum.
• Structure of skeletal muscle-


  myofibrils in muscle fibres made of protein and specialised for contraction

  -lined up in parallel to provide maximum force when they all contract together

  Made up of 2 types ofprotein filaments:

  actin - thinner filament consisting of two strands twisted around eachother

  myosin - thicker filament consisting of long rod-shaped fibres

  
• Histology of skeletal muscle

  -individual muscle fibres

  - long and thin multinucleated fibres that are crossed with a regular pattern of fine red and white lines

  -highly structured arrangements of sarcomeres

  -streaks of connective and adipose tissue

  -capillaries running in between the fibres
• Myofibrils appearances (bands and zones)

  Light bands- area where actin and myosin filaments do not overlap. only actin is found here.

  Dark bands- presence of thick myosin filaments

  Z -line - line found at centre of each light band.

  distance between adjacent Z-lines is called a sarcomere (shortens when muscle contracts)

  H -zone - lighter coloured region found in the centre of each dark band. only myosin filaments are present at this point (decreases when muscle contracts)

  
• Neuromuscular junction


  Site where the motor neurone meets the muscle fibre and is separated by a gap called the neuromuscular cleft
• What is the purpose of T-tubules


  Penetrates deep in the muscle fibre so it can reach the sarcoplasmic reticulum to release Ca2+. It conducts impulses to the deepest regions of the muscle cell.
• Neuromuscular junction process Pt1

  1. action potential reaches the end of the motor neurone and causes depolarisation.
  2. voltage-gated calcium ion channels open causing calcium ions to diffuse in.
  3. this causes vesicles to move along the cytoskeleton with acetylcholine and fuse out the membrane by exocytosis and acetylcholine is released into synapse.
• Why does acetylcholinesterase break down acetylcholine

  To prevent the muscle being overstimulated and so the action potential is not being constantly regenerated
• Structure of myosin

  Myosin filaments have globular heads that are hinged which allows them to move back and forwards

  On the head is a binding site for actin and ATP

  
• Structure of actin


  Binding sites for myosin heads, covered by tropomyosin which is held in place by troponin

  
• When a myosin head binds to an actin molecule, a ____________ is formed.

  The myosin heads then bends towards the center and this called the ____________ pulling the actin filaments with it.

  The cross-bridge is then broken with the hydrolysis of _______ returning the myosin to its relaxed position.

  When a myosin head binds to an actin molecule, a cross-bridge is formed.The myosin heads then bends towards the center and this called the power-stroke pulling the actin filaments with it. The cross-bridge is then broken with the hydrolysis of ATP returning the myosin to its relaxed position.
• How do actin filaments expose the myosin binding sites

  Ca2+is released by the sarcoplasmic reticulum and binds to troponin on actin filaments causing a conformational change exposing the myosin binding sites
• What happens to the bands of the sarcomere during contraction

  Sarcomere shortens in length (distance between z lines decreases)

  A (dark) band remains the same

  I (light) band has shortened

  H zone has shortened

  
• Sliding filament model summary

  1) The active site on actin is exposed as Ca2+ binds with troponin

  2) The myosin head forms a cross-bridge with actin

  3) During the power-stroke, the myosin head bends, and ADP and Phosphate are released pulling actin filaments over

  4) A new molecule ofATP binds to myosin head causing the cross-bridge to detach

  5)ATP hydrolyses to ADP and Phosphate using ATPase causing myosin head to go back to the normal relaxed position.