Neuroanatomy Part 1

Question 1

Nervous System

Answer 1

Central Nervous system (CNS)
 >. Brain
 >. Spinal Cord
Peripheral Nervous System (PNS)
 >. Sensory & Moter Cells
 >. Somatic Nervous System
 >. Autonomic Nervous System
 >. Sympathetic 
 >. Parasympathetic

Question 2

CNS: Spinal Cord

Answer 2

•3 main functions

• Conduit for sensory information (via afferent pathways)
• Conduit for motor information (via efferent pathways)
• Centre for coordinating certain reflexes

Pathway for sensory impulses to brain and motor impulses from the brain

Question 3

CNS = Pathways

Answer 3

> . Afferent Nerve fibres carry signals from Sensory organs toward CNS.
. Efferent nerve fibres carry signals away from CNS to muscles or glands.

Question 4

PNS: Somatic Nervous System

Answer 4

•12 pairs of cranial nerves
•31 pairs of spinal nerves
•Sensory and motor components
•Sensory (smell, vision, hearing and balance),
-Afferent neurons carry impulses from sense organs to CNS
•Motor neurons (e.g.,swallowing, eye movement)
-Efferent neurons carry impulses from CNS to muscles and organs

Question 5

The Cranial Nerves

Answer 5

•12 pairs (i.e., bilateral) of nerves that run from the brain stem (3-12) and basal forebrain (1 and 2).
•Named and numbered based on location from front-to-back of brain.
•Relay information between the CNS and the body, particularly regions of the head
and neck.
•Important for clinical diagnosis and localization of injuries (tumours, stroke, inflammation)

Question 6

Sympathetic Nervous System

Answer 6

> . Thoracic and lumbar spinal regions
. Innervates different organs of the body
. Main function to mobilize body’s responses under stressful circumstances
. “fight or flight” responses such as increasing heart rate, relaxing bladder control, dilating pupils

Question 7

Parasympathetic Nervous System

Answer 7

> . Arises from the cranial nerves and from sacral spinal regions
. “Rest and Digest” functions such as increasing gastric secretions and peristalsis, slowing heart rate and decreasing pupil size

Question 8

Blood Supply to CNS

Answer 8

Supplies oxygen and glucose in order to maintain neuron functioning

• Supplied by two paired sets of arteries
• Internal Carotid Artery (ICA)
• Supplies anterior portion of brain and internal structures)
• Vertebral Artery
• supplies posterior portion of the brain
• Combines to form the Basilar artery

Blockage to one of these arteries results in stroke

Question 9

Blood Supply: Circle of Willis

Answer 9

Circle of Willis: a ring of blood vessels

• Interconnects the internal carotid and vertebral-basilar systems
• Allows collateral blood flow to anterior and posterior cerebrovascular system

Question 10

CNS Protection: Meninges

Answer 10

• “menix” meaning membrane, surrounds entire brain and spinal cord.
• Composed of 3 different membranes from the outermost layer inward Dura Mater, Arachnoid Mater and Pia Mater
• Stabilizes the shape and position of the CNS during head and body movement.

Question 11

CNS Protection: Cerebrospinal Fluid

Answer 11

Secretion of the choroid plexus

• Occupies space between arachnoid matter and pia matter surrounding the brain
• Adult = 125-150 mL per day
• Disruption/blockage of CSF circulation can cause medical conditions such as Hydrocephalus

Question 12

CNS Protection: Blood Brain Barrier (BBB)

Answer 12

Barrier which separates circulating blood from CSF

• formed by brain endothelial cells; connected by tight junctions
• Protects CNS by preventing large molecules: bacteria from entering brain
• Regulates transport of essential smaller molecules in order to maintain a stable Environment.

Question 13

Anatomical Planes

Answer 13

Sectioning the brain

Sagittal: Divides the left-side of the brain from the right side.

Coronal: Divides the anterior (front) part of the brain from posterior (back) part.

Question 14

Hindbrain: Metencephalon

Answer 14

> . Cerebellum(little brain):motor control coordination, balance, posture/equilibrium, implicit learning and memory (motor actions)

> . Cerebellar Peduncles (3 connective tracts between cerebellum and brain stem)

> . Pons bridge like structure (axons) connects medulla to midbrain (life-support functions; sleep, heart rate, breathing, arousal (reticular activating system) and crossed afferent (sensory) and efferent (motor).

Question 15

Hindbrain: Myelencephalon

Answer 15

Medulla :composed of Myelinated tracts, carries signals
between brain and the rest of body.

Pyramids: on the surface of the medulla. Carry signals for voluntary movement
from cerebral hemispheres to spine

Olives: Clusters of nuclei connected to cerebellum.

Reticular Formation: network of nuclei in the central region of brainstem,
(sexual arousal, alertness, attention)

Question 16

Reticular Activating System & Reticular Formation:

Answer 16

> . Reticular activating system (RAS)
Regulates states of consciousness complex network of loosely composed neurons

Most influential component is the:
>. Reticular Formation
Extends through core of brain stem between medulla & midbrain primary function; regulate states of consciousness damage may lead to coma or death

Question 17

Midbrain: Mesencephalon

Answer 17

> . Tectum
- Forms roof of midbrain- comprised of two pairs of nuclei
-Superior Colliculi (large rounded mass of grey matter in roof rostral midbrain)
-visual cortex plays a role in visual attention and reflexes
-Inferior Colliculi
(large rounded mass of grey matter found in roof of caudal midbrain)
-major link in the auditory system , thus plays a major role in auditory attention

> . Tegmentum(covering)
General umbrella term for the area anterior to the ventricular spaces of medulla, pons and midbrain
- Forms floor of midbrain
-Red nuclei (involved in cerebellar circulation: sensorimotor system)
-Periaqueductal Gray (suppression of pain and in defense behaviour)
-Substantia Nigra (sensorimotor)

Question 18

Midbrain: Substantia Nigra

Answer 18

•Large nucleus in midbrain, interposed between the red nucleus and cerebral 
peduncles
•Controls voluntary movement
•Produces neurotransmitter dopamine
•Regulates mood

•Parkinson’s Disease results from deterioration of neurons in Substantia Nigra