1. Label, on a diagram of the brain, the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemispheres.

2. Outline the functions for each of the parts of the human brain in E.5.1.

• medulla oblongata: controls automatic and homeostatic activities, such as:
  • swallowing
  • digestion & vomiting
  • breathing
  • heart activity
• cerebellum: coordinates unconscious functions, such as:
  • body movements
  • posture and balance
• hypothalamus: maintains homeostasis, coordinating the nervous and endocrine systems:
  • regulates, appetite, thirst, body temperature, and sleep
  • secretes hormones of the posterior pituitary
  • secretes hormone releasing factors regulating the anterior pituitary
• pituitary gland:
  • posterior lobe stores and releases hypothalamic hormones
  • anterior lobe produces, stores, and secretes many hormones regulating many body functions
• cerebral hemispheres:
  • act as integrating center for high complex functions, such as:
  • memory, learning, emotion, language, reasoning

3. Explain how animal experiments, lesions and fMRI (functional magnetic resonance imaging) scanning can be used in the identification of the brain part involved in specific functions, providing one specific example of each.

animal experiments:

• surgical procedures allow access to brain
• experiments performed on live animals so that brain is functioning
• effects of experiments observed during and/or after experiment
• specific example: rats
  • research into visual impairments such as strabismus (‘cross eye’)
  • induced by covering the eye with material or stitching the eye shut
  • monitor visual development
• ethical issues related to suffering of animals, and sacrifice of animals

lesions:

• damage to specific brain regions
  • injury by accident/war
  • stroke
  • tumor
• allow deduction of location of specific brain functions
• specific example: stroke
  • lesion in Broca's area in left cerebral hemisphere
  • causes dysphasia, inability to speak
  • but reading and writing are unaffected

fMRI

• subject placed in scanning machine which measures blood flow to specific brain areas
  • 1st: high resolution
  • 2nd: series of low resolution while subject is given stimulus
• specific example:
  • subject view visual object moving across a screen and moves a cursor to track its movment
  • fMRI indicates strong activation in cerebellum
  • because cerebellum coordinates eye and hand movements

4. 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

blood flow to gut

• sympathetic:
  • blood vessels constricted, decreasing blood flow to gut
• parasympathetic:
  • blood vessels dilated, increasing blood flow to gut

iris of the eye

• sympathetic:
  • radial muscles contract, dilating the pupil to receive more light
• parasympathetic:
  • circular muscle fibers contract, pupil constricts, protecting retina from too much light

5. Explain the pupil reflex.

• 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

6. Discuss the concept of brain death and the use of the pupil reflex in testing for this.

• pupil reflex can be tested on comatose patients
• if a patient's pupils do not constrict when a light is shone into the eyes,
  • it suggests serious damage to the brain stem/medulla oblongata
  • patient is unlikely to recover
• if a patient's pupils do constrict when a light is shone into the eyes,
  • the patient may be in a coma because of damage to the cerebral hemispheres
  • and may recover some or all functions
• therefore, the pupil reflex is diagnostic
  • comatose patients with brain stem death are often allowed to die
  • comatose patients without brain stem death are often kept alive in hopes of recovery

7. Outline how pain is perceived and how endorphins can act as painkillers.

perception of painful stimuli:

• sensory neurons send action potential from periphery to dorsal horn of spinal cord
  • nociceptors
  • mechanoreceptors
  • thermoreceptors
• synapse between sensory neuron and ascending spinal neuron
  • ascending fibers transmit message of pain to various brain locations
  • neurotransmitter = substance P
  • excitatory neurotransmitter released by pre-synaptic neuron
  • increases Na+ permeability in post-synaptic membrane

• endorphins (enkephalins) = pain-inhibiting neurotransmitters
  • produced by reticular formation in brain
  • descending fibers synapse at the spinal cord dorsal horn
  • release endorphins into synapse between sensory neurons and ascending pain neurons
  • endorphins have specific receptor sites on post-synaptic neurons
  • inhibitory action
    • open K+ channels
    • close Ca+2 channels
  • hyperpolarizing post-synaptic membrane
  • act as pain killers by inhibiting pain signals along ascending pain neurons