Physiology Revision - Brain Basic Structure

Question 1

What are the 4 forms of intracellular communication?

Answer 1

Hormones - produced in and secreted from endocrine glands to act on target cells through the blood

Neurotransmitters -chemical messenger release from dendrites to other neurons, muscle or gland cells through diffusion across extracellular membrane

Paracrine substances - chemical messenger synthesized by cells and released into extracellular fluid for a local response communication

Autocrine substances - Chemical messenger secreted by the cell and acts upon the very same cell

Question 2

What is the structure of the brain/NS?

Answer 2

CNS - Brain and spinal cord as an integrative and control center

PNS - Cranial and Spinal nerves as the communication line btw the CNS and the periphery

Branches to either:

Motor (efferent) division - Motor nerve fibers that conduct impulses from the CNS to the effectors

or

Sensory (afferent) division - Somatic and visual sensory nerve fibers that conduct impulses from periphery receptors to the CNS

Branches from the Motor division:

Autonomic NS - Visceral motor conducts impulses form the CNS to the cardiac muscles, smooth muscle and glands

Somatic NS - Somatic Motor conducts impulses from the CNS to skeletal muscles

Branches from Autonomic division:

Sympathetic division

Parasympathetic division

Question 3

What are the two major types of cells in the NS?

Answer 3

Neurons - make up the majority of the NS

Glial cells - non-neuronal cells in the NS that maintain homeostasis, form myelin, and provide support/protection for neurons

Question 4

What are the 5 types of Glial cells and what is their function?

Answer 4

Astrocytes:

• Regulate glucose, ion concentrations and neurotransmitter uptake around neurons
• Repair the NS
• Maintenance of the BBB
• Vasomodualtion around brain

Oligodendrocytes:

• Produce myelin sheath in the CNS
• One process only myelinates a single segment of the axon

Schwann Cells:

• Produce myelin sheath in the PNS
• Assists in regulation and regrowth of axons

Microglia cells:

• Make up the brain’s immune system
• Scavenge the CNS for plaques, damaged cells and infectious agents (damaged cells release K+ which is detected by the microglia cells)

Ependymal Cells:

• Make up the ependymal membrane; a thin membrane lining the central canal of the spinal cord and ventricles
  -Ependymal cells produce cerebrospinal fluid

Question 5

What are the 5 evolutionary divisions of the brain? List from Rostral (beak) to Caudal (tail)

Answer 5

Telencephalon - Forebrain; consists of the Cortex and Basal Ganglia

Diencephalon - Interbrain; consists of the thalamus

Mesencephalon - Midbrain

Rhombencephalon - Also divided into the Metencephalon (afterbrain) and the Myelencephalon (spinal brain)

Hindbrain; consists of the medulla, pons and cerebellum

Spinal Cord

Question 6

What does the medulla do and where is it?

Answer 6

The medulla controls basic motor functions including:

Cardiac functions - central chemoreceptors sense O2 level in the brain and change heart rate and blood pressure

Respiratory functions - chemoreceptors sense change in blood and increase breathing rate

Reflexes - vomiting, coughing, sneezing and swallowing

It is located below the pons and above the spinal cord.

Question 7

What does the pons do and where is it?

Answer 7

The pons acts as a relay station between the forebrain in the cerebral cortex and the cerebellum.

Its nuclei primarily deal with:

• Sleep
• respiration
• swallowing
• bladder control
• hearing
• equilibrium
• taste
• eye movement
• fascial expressions/sensations
• posture

It is located above the medulla and below the midbrain

Question 8

What does the cerebellum do and where is it?

Answer 8

The cerebellum’s main function is:

Coordination of movements (especially across multiple joints)
Maintenance of balance and posture
Contributes to eye movements
Motor learning

The cerebellum is densely packed and contains more neurons than the cortex. It is located below the occipital lobe of cortex

Question 9

What parts of the brain are conserved through evolution?

Answer 9

The hindbrain:

Medulla, Pons and Cerebellum

Question 10

What does the Midbrain do and where is it located?

Answer 10

The midbrain controls eye movements, auditory and visual processing

• The tectum controls rapid orienation of the head and neck
• Superior colliculus controls vision and eye movements
• Inferior colliculus associated with sound

Located above the pons

Question 11

What part of the Basal Ganglia is found predominantly in the midbrain?

Answer 11

The substantia Nigra

• Helps control movements and is associated with Parkinson’s disease

Question 12

What does the thalamus do and where is it located?

Answer 12

The thalamus acts as a relay station for sensory info ascending to the cerebral cortex

It is composed of thalamic nuclei

Every sensory system (except olfactory) includes a thalamic nucleus in the pathway btw the sensory system and the associated cortical area

It is located above the midbrain

Question 13

What does the hypothalamus do and where is it located?

Answer 13

The hypothalamus is a nervous and endocrine organ that maintains homeostasis through autonomic control of sensory and motor visceral muscles and glands

Located adjacent to the thalamus

Question 14

What percentage of the body’s total cardiac output does the brain consume?

Answer 14

10-19%