CH3&4 (2)

• What do chemoreceptors detect in the blood?

  Concentrations of gases, mainly O2 and CO2
• Where are chemoreceptors located?

  In the nose, mouth, and certain blood vessels
• What stimulates chemoreceptors?

  Scent, taste, pH blood levels, O2, and CO2 concentration
• What do internal chemoreceptors sense?

  Composition of body fluid, including O2, CO2, and pH levels
• What do touch receptors detect?

  pressure or vibrations
• Where are touch receptors mostly located?

  skin
• What are the two types of touch receptors based on sensitivity?

  Peripheral (light touch) and Central (pressure and vibrations)
• The adaptability feature of touch receptors?

  They become less aware of hair follicle movement after a short time
• Pain receptor location


  Every organ except the brain
• Pain receptor stimulation


  heavy cuts, bumps, heat and chemicals
• Pain receptor adaptability


  Non adaptable as a protective feature
• Properties of a reflex arc

  • A stimulus is required
  • Rapid response
  • Occurs the same way each time
• Why is a reflex arc considered involuntary?

  It involves the spinal cord, not the brain, as a form of protection
• Unconscious Control

  Nerve impulses are sent to the brain after the effector has initiated a response.
• Awareness time of a response 


  after the response has occurred
• innate reflexes


  determined genetically (present at birth) for protection
• acquired reflexes

  Reflexes learnt through constant repetition.

  Muscular adjustements required to maintain balancefor riding a bike.
• 3 Sensations Felt if there was damage to the spinal neural pathway

  1. numbness below the injury

  2. intense pain that radiates along the affected neural pathway

  3. inability to control bowel or bladder function as nerve signals are disrupted.
• Outer layer of cerebrum

  consists of gray matter - allowing the cortex to contain 70% of all CNS neurons.
• Inner layer of cerebrum

  consists of white matter folded into patterns, increasing the surface area.

  o Contains nerve fibres surrounded by a myelin sheath

  o Contains 3 nerve Fiber tracts:

  1. Tracts that contain various areas of the cerebral cortex within the same hemisphere of the brain.

  2. Tracts that carry nerve impulses between hemispheres.

  3. Tracts that connect the cortex to other parts of the CNS.
• Outer layer of cerebellum

  grey matter
• inner layer of cerebellum

  white matter
• Cerebellum function

  Balance and coordination via audio stimuli received by the inner ear.
• Can humans move without the cerebellum?

  Yes, but movement would be spasmodic & jerky
• Corpus callosum function


  Wins the left and right hemispheres of the brain, providing a communication path between the nerve fibres in each
• Medulla Oblongata reflex controls

  swallowing, coughing, breathing
• Functions of the Medulla Oblongata

  • respiratory centre - controlling breathing rate and depth
  • cardiac centre - controlling heart rate and force
  • Vasomotor centre - vasodilation & vasoconstriction of blood vessels
• Function of cerebrospinal fluid

  1. Protection - acts as a shock absorber, cushioning any blows or shocks the spine sustains.
  2. Support - Allows the brain and spinal cord to float.
• Functions of cerebrospinal fluid

  1. acts as a shock absorber
  2. allows the spine to bend
  3. allows the brain and spinal cord to float
  4. Circulates around and through the CNS, carrying nutrients to the brain and wastes away from the brain before entering the blood capillaries
• Dorsal route structure


  ganglion of sensory neurons
• ventral route structure 


  ganglion of motor neurons
• What happens if dorsal route is cut?

  No sensory information is received, but movement still occurs as motor neurons originate in ventral root
• SC gray matter

  In central canal

  Contains cerebrospinal fluid

  Unmyelinated nerve axons
• Ascending tract in the SC


  Transmits nerve impulses to the brain (dorsal root)
• Descending tract in the SC

  Transmits nerve impulses from brain to effector (ventral root)
• Synapse 


  the junction between branches of two adjacent cells
• Role of acetylcholine (3)

  1. muscle contraction at synapse by binding to receptor on postsynaptic muscle cell.

  2. Regulates involuntary muscle (heart rate, digestion and glandular secretion)

  3. Plays a role in learning & memory (parietal lobe).
• Functions that can be used to distinguish types of neurons (4)

  • shape and structure
  • neurotransmitter
  • function
  • location
• Role of sodium channels 


  Initiate an action potential
• Result of blocked sodium channels

  Prevent the depolarization phase of the action potential from occurring. As a result, the neuron would fail to generate and propagate the electrical impulse along its axon. Without the propagation of action potentials, communication between neurons would be disrupted, leading to a loss of sensation, movement, and other neurological functions.