The Brain (MODULE 5) Flashcards
Structural organisation of the brain:
Central nervous system and peripheral nervous system
Central nervous system (CNS):
Brain and spinal cord
Peripheral nervous system (PNS):
All the neurones that connect the CNS to your body
Functional organisation of the brain:
Somatic nervous system and autonomic nervous system
Somatic nervous system:
System under conscious control/voluntary actions. The SNS carries impulses to muscles
Autonomic nervous system:
System under subconscious control/automatic actions. This system works constantly, and carries impulses to glands, smooth muscle and cardiac muscle
Example of somatic nervous system:
Limb movement
Example of autonomic nervous system:
Heart beat and digestion of food
Division of autonomic nervous system:
Sympathetic nervous system and parasympathetic
Difference between sympathetic and parasympathetic nervous systems:
Sympathetic: increases general activity (increase in heart rate)
Parasympathetic: decreases general activity (decrease in heart/decrease in breathing rate)
Gross structure of the brain:
Cerebrum, cerebellum, medulla oblongata, hypothalamus, pituitary gland
Cerebrum:
Controls voluntary actions, such as learning, memory, personality, conscious thought
Cerebellum:
Controls unconscious function such as posture, balance and non-voluntary movement. Coordinates movement
Medulla oblongata:
Autonomic control, such as controlling heart and breathing rate
Hypothalamus:
Thermoregulation and osmoregulation of blood plasma, producing hormone, controlling complex behaviour patterns (feeding, sleeping)
Pituitary gland:
Stores and releases hormones that regulate several body functions
Anterior pituitary:
Front section of pituitary gland, produces 6 hormones including LH and FSH
Posterior pituitary:
Back section of the gland, stores and releases hormones produced by the hypothalamus including ADH
Basic reflex arc:
Receptor -> sensory neurone -> relay neurone -> motor neurone -> effector
Examples of reflex arcs:
Knee-jerk reflex (spinal reflex), blinking reflex (brain reflex)
Knee-jerk reflex:
- leg is tapped below the kneecap (patella)
- stretch of patellar tendon acts as a tendon
- causes extensor muscles (top of thigh) to contract
- relay neurone inhibits the motor neurone in the flexor muscle, causing it to relax
- the SIMULTANEOUS relaxation and contraction causes the leg to kick
What does the absence of the knee-jerk reflex indicate?
Nervous problems (multiple kicks may indicate cerebellar disease)
Purpose of the knee-jerk reflex:
Maintain posture and balance
Blinking reflex:
- cornea stimulated
- impulse triggered along sensory neurone on the fifth cranial nerve
- impulse passes along relay neurone in the lower brain stem
- motor neurone initiates motor response to close the eyelids
- this is deemed a ‘consensual response,’ so both eyelids close
Purpose of the blinking reflex:
Keep cornea safe from damage due to foreign bodies, protect lens and retina from very bright light
What does the presence of the blinking reflex indicate?
Lower brain stem function
Reflex survival importance:
- being involuntary responses: decision making not involved, so more energy can be used for complex responses
- not being learnt: present at birth for immediate protection
- extremely fast: short reflex arc with only one or two synapses
