Lecture 4: Anatomy of the nervous system

Question 1

What are the Anatomical directions in the vertebrates?

Answer 1

• Lateral: Towards the side
• Medial: Towards the midline
• Dorsal: Toward the back
• Ventral: Toward the stomach
• Anterior: Toward front end
• Posterior: Toward rear end
• Directions in the cerebral hemispheres rotated by 90’ in comparison to those of spinal cord.

Question 2

What is the Midsagittal section?

Answer 2

Section cut down the centre of the brain.

Question 3

What is the Somatic nervous system?

Answer 3

• Interacts with external environment.
• Controls voluntary muscles and conveys sensory information to the CNS.
• Afferent: from skin, skeleton muscles.
• Efferent: Motor signals from CNS to skeleton muscles.
• Conscious and voluntary.

Question 4

What is the Autonomic nervous system?

Answer 4

• Regulates body’s internal environment.
• Controls involuntary muscles.
• Afferent: internal sensory signals to CNS.
• Efferent: Motor signals from CNS to internal organs.
• Unconscious and automatic.

Question 5

What is the sympathetic Nervous system?

Answer 5

• Prepares the organs for vigorous activity.

* Increases breathing and heart rate, decreases digestive activity.

Question 6

What is the Parasympathetic Nervous system?

Answer 6

• Promotes energy - conserving, non - emergency functions.

* Generally does the opposite of sympathetic activities.

Question 7

What is the spinal cord?

Answer 7

• Communicates with sense organs and muscles below the head.
• Segmented structure
• Sensory nerves: enter
• Motor Nerves: Exit.
• If cut, brain loses sensation from that segment and all segments below.
• Simple, reflexive behaviours can take place on the level of the spinal cord.

Question 8

What is the function of the Hindbrain?

Answer 8

• Medulla
• Tracts carrying signals between rest of the brain and body.
• Controls some vital reflexes (breathing, heart rate, vomiting).
• Reticular formation
• Plays important role in arousal, sleep, attention, movement, cardiac and circulatory responses.
• Pons
• Axons from each side of the hemisphere cross.
• Cerebellum
• Important sensorimotor structure - coordination of movements.
• Seems also involved in cognitive functions.

Question 9

What is the function of the Midbrain?

Answer 9

*Tectum
-Superior colliculus: visual function.
-Inferior colliculus: Auditory function.
(Dorsal)
*Tegmentum
-Sensorimotor function, part of the system that deteriorates in parkinson’s disease.

Question 10

What is the function of the Forebrain - Diencephalon?

Answer 10

• Thalamus
• Sensory relay to the cerebellum (except for olfactory information).
• Hypothalamus
• Important for regulation of motivated behaviours.
• maintanance of homeostasis.
• Regulates release of hormones from pituitary gland.

Question 11

What is the Forebrain - Telencephalon?

Answer 11

• Largest division of the human brain.
• Initiates voluntary movement, interprets sensory input, mediates complex cognitive processes.
• Main parts: cerebral cortex, basal ganglia, limbic system.

Question 12

What is the function of the Forebrain - Telencephalon?

*Basal ganglia

Answer 12

• Several structures that play a major role for voluntary motor responses.
• e.g. pathway from substantia nigra to striatum is deteriorated in Parkinson’s disease.
• Electrodes implanted deep inside the brain.
• Targeted brain regions electrically stimulated.
• Result: Reduction of tremor.

Question 13

What is the function of the Forebrain - Telencephalon?

*Limbic system

Answer 13

-Regulates of motivated behaviours.
-Amygdala, hippocampus, cingulate, cortex and others.
*Cerebral Cortex
-Outer surface of cerebral hemispheres
-4 lobes
-Deeply convoluted to increase surface of the cortex
> Large furrows: fissures
> Small furrows: Sulci
> Ridges between furrows: Gyri
-Neurons communicate across hemispheres mainly through the corpus callosum.

Question 14

What is the function of the Forebrain - Telencephalon?

*Occipital Lobe

Answer 14

• Primary visual area
• Destruction of any part of the primary visual cortex causes cortical blindness in the related part of the visual field.

Question 15

What is the function of the Forebrain - Telencephalon?

*Parietal Lobe

Answer 15

• Receive sensation from touch, muscle stretch and joint receptors.
• Lesions often result in hemispatial neglect, (e.g. damage to the right hemisphere causes tendency to ignore the left visual field).
• Not an deficit in perception or sensation, but in attention.

Question 16

What is the function of the Forebrain - Telencephalon?

*Plasticity of the brain

Answer 16

• Somatosensory cortex undergoes substantial reorganisation after the loss of sensory input.
• Can lead to phantom limb sensation.
• Learned adjustments in behaviour.

Question 17

What is the function of the Forebrain - Telencephalon?

*Temporal lobe

Answer 17

• Primary target for auditory information.
• Left temporal lobe relevant to understanding language.
• Medial part: Memory (hippocampus)
• Inferior part: Complex aspect of vision (e.g. facial recognition).

Question 18

What is the function of the Forebrain - Telencephalon?

*Frontal lobe

Answer 18

• Primary motor cortex
• Controls voluntary movement of the body.
• Prefrontal cortex:
• receives and integrates input from all sensory systems.
• Higher cognitive functions (working, memory, planning).
• prefrontal lobotomy - surgical disconnection of the prefrontal cortex from the rest of the brain (1940s/50s)

Question 19

What equipment is used to measure the brain?

Answer 19

• PET - 3D image of the brain.
• fMRI - measures brain activity, looks at blood flow.
• EEG

Question 20

What are the effects of brain damage?

Answer 20

• Damage in the left frontal cortex
• Language impairment
• Discovery of Broca’s & Wernicke’s areas.
• Problem: few cases and damage rarely localised.
• visual lesion via magnetic stimulation.
• Only temporary.
• The brain is symmetrical (anatomy).
• The brain is asymmetrical (function).
• Split brain research: corpus callosum is severed in some epileptic patient (prevents seizure to travel to the 2nd hemisphere) *Sperry.