animal responses

• Mammalian nerve system


  1. Made up of the peripheral nervous system and the central nervous system

  2. Peripheral nervous system includes receptors, sensory and motor neurons

  3. Central nervous system is the coordination center including the brain and spinal cord
• Categories of the nervous system

  • Autonomic nerve system
  • Somatic nerve system
• Autonomic nerve system


  • Works constantly and subconsciously, includes activities like digestion
  • No conscious control over activities
• Somatic nerve system


  • Consciously controlled, voluntary, for example, moving by choice
• The human brain is made up of billions of neurons and coordinates responses
• Key structures of the human brain

  • Cerebrum
  • Cerebellum
  • Medulla oblongata
  • Hypothalamus
  • Pituitary gland
• Cerebrum


  • Largest part of the brain, outer layer known as the cerebral cortex, controls conscious thoughts, language, intelligence, personality, high-level functions, and memory
• Cerebellum


  • Coordinates movement, muscles, and balance
• Medulla oblongata


  • Center of control for unconscious activities like breathing and heart rate
• Hypothalamus


  • Responsible for homeostasis, temperature, and water balance
• Pituitary gland


  • Master gland, secretes hormones to coordinate responses like the Easter cycle and osmoregulation
• Reflex is a rapid automatic response to protect from danger, involving only three neurons and two synapses
• Reflex arc

  Stimulus detected by receptor, impulse passed along sensory neuron to relay neuron, then to motor neuron connected to an effector for response
• Fight or flight response in animals prepares them to either fight or run away from potential threats
• Control of heart rate

  Medulla oblongata in the brain controls heart rate via the autonomic nervous system, sympathetic system increases heart rate, parasympathetic system decreases heart rate
• The brain controls the heart rate via the autonomic nervous system


  There are two parts: one linked to the cyanoatrial node to increase the heart rate by the sympathetic nervous system, another that decreases the heart rate by the parasympathetic nervous system
• The heart rate changes in response to pH and blood pressure

  Stimuli are detected by chemoreceptors if it's a change in pH and pressure, or baroreceptors if it's a change in blood pressure
• Receptors for stimuli detection

  • Chemoreceptors
  • Baroreceptors
• Carbon dioxide and lactic acid decrease the pH of the blood
• Response to pH

  An increase in the heart rate to remove carbon dioxide and lactic acid rapidly to prevent enzyme denaturation
• Response to pressure

  If blood pressure is too high, more impulses via the parasympathetic nervous system decrease the heart rate; if blood pressure is too low, more impulses via the sympathetic nervous system increase the heart rate
• Types of muscles

  • Skeletal muscles
  • Cardiac muscle
  • Involuntary or smooth muscle
• Cardiac muscle


  Within the heart, myogenic (does not require input from the nerve system to contract and relax)
• Involuntary or smooth muscle


  Lines organs and blood vessels, causes movement of the contents of an organ or a blood vessel by contracting and relaxing
• Neuromuscular Junction


  Where a neuron meets the muscles, acting as the effector in the response arc
• Muscles act in antagonistic pairs against an incompressible skeleton to create movement
• Myofibrils are made up of sarcomeres, which consist of the proteins actin and myosin
• The muscle fibers are made up of millions of myofibrils, collectively bringing about the force for movement
• The sarcomere consists of actin and myosin proteins
• During muscle contraction, the A band remains constant, the H zone decreases, the I band decreases, and the Z lines move closer together
• Sliding filament theory explains muscle contraction: an action potential stimulates a response, calcium ions enter, causing tropomyosin to move and uncover binding sites on actin
• Sliding filament theory


  Action potential reaches the muscle, calcium ions enter and cause tropomyosin to move, uncovering binding sites on actin. Myosin heads bind to actin forming a cross-bridge structure, creating tension and pulling the actin filament along the myosin. ATP binds to myosin head causing it to detach from actin. ATP is hydrolyzed by ATPase to release energy for myosin head to return to original position. Process repeats sliding actin closer together, contracting the muscle
• Role of ATP and phosphocreatine


  Active muscles need a high concentration of ATP. Phosphocreatine stored in muscles provides phosphate to regenerate ATP from ADP