E.4b Neurotransmitters

depression

• caused by deficiency of norepinephrine (NE) and/or serotonin (ST)
• psychoactive drugs can increase the levels of NE/ST at synapses
• increase in secretion of NE/ST from pre-synaptic neurons
• suppression of NE/ST deactivating enzymes at post-synaptic neurons
• inhibition of NE/ST uptake by pre-synaptic neurons
• elevate mood in normal people
• alleviate depression in the chronically depressed

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E.4a Synapses

EPSPs: excitatory post-synaptic potentials

• post-synaptic neurons have receptor proteins specific to excitatory neurotransmitters
• binding neurotransmitter makes post-synaptic membrane permeable to Na+, which moves across post-synaptic membrane
• causing depolarization of the post-synaptic membrane
• enzymes catabolize neurotransmitters
  • monoamine oxidase catabolizes norepinephrine
  • acetylcholine esterase catabolizes acetylcholine
  • examples of excitatory neurotransmitters
    • epinephrine
    • dopamine
    • serotonin

E.5b Brain Function

Explain sympathetic and parasympathetic control of the heart, movements of the iris, and flow of blood to the gut.

autonomic nervous system:

• sympathetic:
  • fight-flight-excercise
• parasympathetic:
  • restorative, resting, digesting

heart

• sympathetic:
  • heart rate accelerates, pumping more blood to muscles
• parasympathetic:
  • heart rate slows, body relaxes, less blood needed to muscles

E.5a Brain Structure

pupil reflex: when a bright light shines into one eye, the pupils of both eyes normally constrict

• retina detects light intensity
• impulses to brain in optic nerve
• brain stem/medulla controls the reflex
• sympathetic system causes dilation
• parasympathetic system causes constriction
• sympathetic neurons are in spinal nerve T1
• parasympathetic neurons are in cranial nerve III
• pre- and postganglionic fibers of symp/parasymp
• neurotransmitters of symp/parasymp
• polysynaptic reflex

E.2d Ears

eardrum

• sound waves cause eardrum to vibrate towards and away from middle ear
• eardrum transmits mechanical vibration of air molecules to middle ear

bones of middle ear

• ossicles = series of very small bones
  • 1st attached to eardrum
  • 3rd attached to oval window
  • muscles attached to ossicles protect from loud sound
    • by contracting to damp down vibrations
• amplify sound x20 by acting as levers:
  • reduce sound wave amplitude
  • increase sound wave force
  • oval window’s small size relative to eardrum increases amplification

E.2c: Visual Processing

edge enhancement:

• occurs within the retina
  • two types of ganglion cell, each stimulated when light falls on a small circular area of retina called the receptive field
  • on-center ganglion cells
    • ganglion is stimulated if light falls on the center of the receptive field
    • but this stimulation is reduced if light also falls on the periphery
  • off-center ganglion cells
    • light falling on the periphery of the receptive field stimulates the ganglion cell
    • if light also fall on the center of the receptive field, stimulation is reduced
  • both types of ganglion cell are therefore more stimulated if the edge of the light/dark is within the receptive field

E.2b Retina

thermoreceptors:

• membrane receptor proteins respond to temperature,
• which results in membrane depolarization
• leading to action potentials sent to brain,
• which interprets the sensation,
• e.g. free nerve endings in dermis detect warmth; hypothalamic thermostat detects internal temperature

photoreceptors:

• photopigments change when activated by specific wavelengths of light,
• which results in membrane depolarization
• leading to action potentials sent to brain,
• which interprets the sensation,
• e.g. rods and cones in the retina of the eye

E.2a Eyes

1. Outline the diversity of stimuli that can be detected by human sensory receptors, including mechanoreceptors, chemoreceptors, thermoreceptors and photoreceptors.

mechanoreceptors:

• membrane receptor proteins respond to mechanical deformation,
• which results in membrane depolarization
• leading to action potentials sent to brain,
• which interprets the sensation,
• e.g. Meissner’s corpuscle (light touch), Pacinian corpuscle (deep pressure), hair cells (hearing, balance), aortic baroreceptor (blood pressure)

chemoreceptors:

• membrane receptor proteins bind specific molecules
• which results in membrane depolarization
• leading to action potentials sent to brain,
• which interprets the sensation,
• e.g. olfactory neurons, gustatory cells of taste buds, aortic carotid bodies, hypothalamic glucoreceptors

thermoreceptors:

• membrane receptor proteins respond to temperature,
• which results in membrane depolarization
• leading to action potentials sent to brain,
• which interprets the sensation,
• e.g. free nerve endings in dermis detect warmth; hypothalamic thermostat detects internal temperature

photoreceptors:

• photopigments change when activated by specific wavelengths of light,
• which results in membrane depolarization
• leading to action potentials sent to brain,
• which interprets the sensation,
• e.g. rods and cones in the retina of the eye

11.2b Muscles & Joints

. Outline the functions of the structures of the human elbow joint named in 11.2.2.

• Cartilage: reduces friction between bones where they meet
• Synovial fluid: lubricates joint to reduce friction
• Joint capsule: seals the joint and holds in the synovial fluid
• Humerus: upper arm bone: attachment of biceps and triceps
• Ulna & radius: forearm bones: attachment of biceps and triceps
• Biceps: attaches from humerus to ulna & radius
• Triceps: attaches from humerus to ulna
• Antagonism: biceps and triceps attach across elbow joint; while triceps contracts to to extend arm, biceps relaxes; conversely, while treceps relax and the biceps contract, flexing the arm