Lecture 9: Brain Organization

Reading: Ch 5, sections: organization, cerebral cortex, cerebellum and brainstem, spinal cord Ch 7, section: autonomic nervous system

Conduction speed on myelinated axons ~ 120 m/s

Longest axon ~ meter long (big toe to spinal cord)

Total travel time for a nerve impulse from head to toe: 10 ms + 10 ms + 1-2 ms per synapse = ~ 25 ms

Brain

sensory inputs

motor outputs

Body

Sensory-motor transformation

General Organization

Central Nervous System (CNS)A. Brain

1. Forebraina. Cerebral

Cortexb. Basal

Gangliac.

Thalamusd. Limbic

System2. Brainstem

a. Midbrain

b. Ponsc.

Medulla Oblongata3. Cerebellum

a. Cerebellar Cortex

b. Deep Nuclei

B. Spinal Cord1. Sensory2. Motor

Peripheral Nervous System (PNS)A. Somatic Division

1. Sensory2. Motor

B. Autonomic Division1. Sympathetic2. Parasympathetic3. Enteric

cerebrum

diencephalon

Human Brain

Gray Matter vs. White Matter (not in notes)

Brain Spinal Cord

Gray Matter – Nervous Tissue that primarily contains cell bodies

White Matter – Nervous Tissue that primarily contains axons

Graymatter

Cerebrum - portion of the CNS largely responsible for all of the higher cognitive, sensory and motor

functions of the brain.

Cerebral Cortex - the outer, highly folded surface of the cerebrum.

CNS\Brain\Forebrain\Cerebrum\Cerebral Cortex:

4 Lobes - Frontal, Parietal, Temporal, and Occipital Lobes

CNS\Brain\Forebrain\Cerebrum\Cerebral Cortex:

“Functional Localization”

Primary Visual Cortex – Occipital LobePrimary Auditory Cortex – Temporal Lobe

Primary Motor Cortex – Frontal LobeSomatosensory Cortex – Parietal Lobe

Examples:

Sensory Homunculus

CNS\Brain\Forebrain\Cerebrum\Cerebral Cortex (cont.)

- orderly mapping of body parts- overrepresentation of regions with great acuity (hand and head)

General Theme:

Motor Homunculus

CNS\Brain\Forebrain\Cerebrum\Cerebral Cortex (cont.)

Basal Ganglia Set of large nuclei lying in the center of the brain, highly connected with the cerebral cortex the thalamus.

(see next slide)

Thalamus Large nucleus, composed of many smaller subnuclei, lying in the center of the brain just posterior to the Basal Ganglia. Functions cooperatively with, and is highly connected to, the cerebral cortex.

(see next slide)

CNS\Brain\Forebrain\Cerebrum:

CNS\Brain\Forebrain\Diencephalon:

Basal Ganglia and ThalamusCNS\Brain\Forebrain\:

Limbic System - Collection of nuclei, interconnected to the thalamus and cerebral cortex, that

play a key role in learning, memory and emotions.

CNS\Brain\Forebrain\:

Brainstem - evolutionarily older (so-called reptilian) portion of the CNS, essential for the maintenance of life and many autonomic functions.

1) Midbrain - the upper portion of the brainstem.

2) Pons - the middle portion of the brainstem.

3) Medulla Oblongata - the lower portion of the brainstem continuous with the spinal cord.

CNS\Brain\Brainstem\:

CNS\Brain\Brainstem\:

Midbrain, Pons, and Medulla Oblongata

Cerebellum Large neural lobe located on the lower posterior region of the brain, involved in numerous functions, particularly important in the control of motor coordination.

CNS\Brain\Cerebellum\:

CNS\Brain\Cerebellum\:

Cerebellar Cortex - The outer, highly folded surface of the cerebellum.

Deep Nuclei - Nuclear structures, analogous to the Basal Ganglia in the cerebrum, that lie below the cortex in the depth of the cerebellum.

CNS\Spinal Cord\:

Spinal Cord - Column of neural tissue from the medulla to the lower end of the spinal column. Contains the input and output pathways of the CNS.

Sensory - subdivision that processes and relays somatic sensory information to the cerebrum.

Motor - subdivision that processes and relays somatic motor information to the somatic musculature.

CNS\Spinal Cord\:

A. Somatic Division - portion of the PNS containing all of the somatic sensory and motor nerves and ganglia.

1) Sensory - somatic sensory nerves and ganglia.

2) Motor - somatic motor nerves and ganglia.

B. Autonomic Division - The portion of the PNS responsible for regulating the involuntary actions of the internal organs.

1) Sympathetic - division of the autonomic nervous system that prepares the body for strenuous physical activity.

2) Parasympathetic - division of the autonomic nervous system that maintains resting functions of the internal organs.

3) Enteric - division of the autonomic nervous system that regulates the functions of the gut.

PNS\

Peripheral Nervous System (PNS) - that portion of the nervous system not located within the skull or the spinal column.

PNS\Autonomic Division\ Neurotransmitters

Parasympathetic System – Acetyl Choline (ACh)Sympathetic System – ACh, …Norepinephrine (NE)/Epinephrine (E)

PNS\Autonomic Division\

Sympathetic division involved with preparing the body for strenuous activity

Parasympathetic division involved with maintaining resting functions