Nervous Responses and Stimuli

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Ball and Socket (Shoulder/Hip) - allows movement in all directions

Gliding Joints (Wrist) - allows a wide range of movement because small bones slide over each other

Hinge Joints (Elbow/Knee) allow movement along one plane ie up and down or left to right

Fixed Joints (Skull) do not allow movement

An Antagonistic Pair - a pair of muscles that work against each tocause movement at a joint

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The Neuromuscular Junction - Cholinergic Synapses

Action Potential in the synaptic knob of the pre-synaptic neurone causes voltage-gated calcium channels to open. Calcium ions diffuse into the synaptic knob.

Calcium ions cause synaptic vesicles of the neurotransmitter acetylcholine to fuse with the pre-synaptic membrane and release the neurotransmitter into the cleft (exocytosis)

Acetylcholine diffuses across the cleft and binds with receptors on the Na+ ion channels in the post-synpatic sarcolemma membrane. The channels open

Na ions diffuse across the postsynaptic membrane into the sarcolemma. this gnrates an excitory postsynpatic potential and if a threshold level is reached, itcauses a wave of depolarisation.

The wave of depolarisation travels down the tubules (T system) and depolarisation then causes the sarcoplasmic reticulum to release Ca2+ ions

The Ca 2+ ions then bind with the muscle fibres and stimulate a contraction

Acetylcholine is quikcly broken down by acetylcholinase so that contraction only occurs when impulses are continuous

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Muscle Contractions

Motor Unit:- Innervation of a cluster of muscle fibres by a single motor neurone ---> the number of muscle fibres in a motor unit is determined by the level of manipulaino required in the muscle

Gradation of Response:- The more motor uits that are stimulated, the greater the force of contraction

Ringer's Solution - keeping whole muscles alive by immersing them in  solution of salts

Twitch - a quick contraction of a muscle follwed by immediate relacation

Tetanus - repeated large stimuli giving a large sustained and powerful contraction

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The Fight or Flight Response

...the perception of a threat to the safety of a mammal leads to a number fo physiological changes that prepare the organism to deal with the threat.

Physiological Changes

  • Pupils dilate
  • Heart Rate and Blood pressure increase
  • Blood glucose levels increase
  • Metabolc rate increases
  • Ventilation rate and depth increase
  • Sweat Production increases
  • Arterioles to the digestive system and skin are constricted whilst those to the muscles and liver are dilated
  • Erector Pili muscles in the skin contracct, making hairs stand up
  • Endorphins (natural painkillers) are released in the brain
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Action of Muscles

volutnary muscles are attached to bones by tendons so that muscle contraction moves the bones at the joints. Tendons are made of tough, inelastic collagen which is continuous with the muscle and periosteum (connective tissue covering the bone)

Muscles only produce force when they contract so movement at a joint requires the coordinated action of at least two muscles. One contracts while the other releases - they are antagonists pairs.

The movement requires a wider range of actions and is under the control of groups of muscles called synergists

  • Cartliage - pads where bones meet reduce friction as bones move
  • Ligament - holds bones together to prevent dislocation
  • Synovial Fluid - lubricates the joint
  • Synovial membrane - secretes the synovial fluid
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