Central Nervous system pt 1

Components of the CNS

Brain and Spinal Cord

Directional Terms

• Rostral: towards the nose

• Caudal: toward the tail

Brain Functions - Vital control & Regulation

• Control heart rate, respiratory rate, and blood pressure

• It regulates the autonomic nervous system and endocrine system

• Controls head movements and sensations via cranial nerves

Brain Function - Higher Cognitive Processes

• Intelligence

• Consciousness

• Memory

• sensory-motor integration

• Emotion Behaviour

• Socialization

Basic Parts and Organization of the Brain

1. Brain stem: midbrain, pons, and medulla oblongata

2. Cerebellum

3. Diencephalon

4. Cerebrum: two hemispheres

Ventricles

• Fluid-filled cavities within the brain, contains cerebrospinal fluid

3 ventricles

1. Lateral Ventricles: cerebral hemispheres, horseshoe-shaped

2. Third Ventricles: diencephalon, connected to lateral ventricles by the interventricular foramen

3. Fourth Ventricle: hindbrain, connects to central canal of spinal cord

Cerebral aqueduct

connects the third and fourth ventricles

Cortex

outer layer of gray matter in the cerebrum and cerebellum

Brain stem functions

• It’s a pathway for fibre tracts between the cerebrum and spinal cord

• Facial and head innervation (10/12 cranial nerves)

• Controls automatic survival behaviour

• Integrates auditory and visual reflexes

Fiber tracts

bundles of axons in the central nervous system (CNS) that connect different areas of the brain and spinal cord.

Midbrain

• between the diencephalon and pons

What does the midbrain contain?

• cerebral aqueduct: central cavity for CSF flow

• Cerebral peduncles: ventral tracts for motor commands (corticospinal)

• Superior Cerebellar peduncles: link midbrain to cerebellum

Corticospinal tracts

The corticospinal tract is a major motor pathway that controls voluntary movements, especially of the limbs and trunk. It carries signals from the cerebral cortex to the spinal cord, where it synapses with motor neurons.

Corpora Quadrigemina

Corpora Quadrigemina is a structure in the midbrain consisting of four rounded protrusions (colliculi). It is responsible for reflexive responses to visual and auditory stimuli.

2 division of the Corpora Quadrigemina

• Superior colliculi (2 upper lobes): visual reflexes, Controls eye movements, tracking moving objects, and coordinating head movements with vision.

• Inferior Colliculi (2 lower lobes): auditory reflexes, Helps detect and localize sounds in the environment.

Periaqueductal Grey Matter

• a gray matter structure in the midbrain, surrounding the cerebral aqueduct

• involved in fight-flight responses and pain modulation

Pigmented Nuclei

The pigmented nuclei are clusters of neurons in the midbrain that contain dark-colored pigments due to their high concentration of melanin and neuromelanin.

What are some Pigmented Nuclei?

• Substantia Nigra: produces dopamine and is linked to motor control

• Red nucleus: coordinates limb movement

Organization of the Mid Brain

• Tectum: Above the cerebral aqueduct and includes the superior and inferior colliculi

  • Sensory processing and reflexes

• Tegmentum: Below the cerebral aqueduct, includes the red nucleus, substantia nigra, and reticular formation

  • Motor control, arousal, movement and sleoo

Midbrain innervation

• III - Oculomotor nerve

• IV- Trochlear nerve

Pons

• A bridge between the midbrain and medulla oblongata

• motor tracts from the cerebral cortex

• contain the Pontine nuclei: which connect the cortex to the cerebellum via middle cerebellar peduncles

Pons - Innervation

• V - Trigeminal nerve

• VI- Abducens nerve

• VII- Facial nerve

Medulla Oblongata

• Caudal part of the brainstem and is continuous with the spinal

• Contain reticular formation

• Contains Autonomic Centers that help with regulating involuntary function.

Autonmic centers of the Medulla Oblongata

• Cardiac

• Vasomotor

• respiratory regulation

Makor Structures of the Medulla Oblongata

• Pyramids: On ventral surface

• Decussation of the Pyramids: crossing over of motor tracts

• Inferior cerebellar peduncles: fibre tracts connecting the medulla and cerebellum

• Olive: contains the inferior olivary nucleus

Innervation of the Medulla Oblongata

• VII - Vestibulocochlear nerve

• IX- Glossopharyngeal nerve

• X- Nerve

• XII- hypoglossal nerve

Cerebellum

• dorsal to pons and medulla

• coordinates body movements and controls posture, balance, and fine motor movements

Cerebellar Hemispheres

• Surface are folded into ridges called folia and are seperaated by fissures

3 subdivision of the Cerebellar hemispheres

1. Anterior lobe

2. Posterior Lobe

3. Flocculonodular lobe

Cerebellar Regions

• Cortex (grey matter)

• Arbor vitae (internal white matter)

• Deep cerebellar nuclei (deep gray matter)

Cerebellar Cortex Functions

• gets input from the

  • Equilibrium sensors

  • Cerebral Cortex

  • Sensory receptors

• Compares intended movement with body positions

• Adjust and fine-tune motor commands

Cerebellar Peduncles ( Superior, Middle, Inferior Peduncles)

• cerebellar peduncles are three pairs of thick bundles of nerve fibres that connect the cerebellum to the brainstem, allowing communication between the cerebellum and other parts of the nervous system

• It’s also an Ipsilateral Pathway meaning fibres travel to and from the same side of the body

Diencephalon

• It’s the core of the forebrain and is surrounded by cerebral hemispheres

• It borders the third ventricle and is primarily grey matter

3 Paired structure of the Diencephalon

1. Thalamus

2. Hypothalamus

3. Epithalamus

Thalamus

• 80% of the diencephalon and has 12 major nuclei

• Relays station for sensory signals to the cerebral cortex

• Afferent impulses synapse in thalamic nuclei

• Nuclei amplify or tone down signals

6 groups of Nuclei

1. Anterior nuclei

2. Lateral nuclei

3. Medial nuclei

4. Intralaminar nuclei

5. Paraventricular (midline) nuclei

6. Reticular nucleus

Hypothalamus

• It’s between the optic chiasm and the mammillary bodies

• The pituitary gland projects inferiorly

• contains 12 nuclei and is the main visceral control centre of the body

Hypothalmus Functions

• Fights - behaviour and control of emotional responses usually aggression or anger

• Flights - emotional responses (stress, fear), ANS control

• Feeding - hunger and thirst

• Fornicating- sexual behaviour, endocrine system

4Fs

Epithalamus

• Located at the roof of the third ventricle

• Contains small nuclei, including the pineal gland

  • Secretes melatonin and is regulated by the hypothalamus

• Role in Controlling Circadian rhythms

Cerebrum

• 83 % of the brain mass

• Contains

  • Fissures: deep grooves

  • Longitudinal Fissures: divides hemispheres

  • Transverse Fissure: Separates cerebrum and cerebellum

Features of the Cerebral Cortex

• Cortex: the outermost layer of the cerebrum, gray matter

• Sulci: grooved indentations

• Gyri: raised ridges

These increase surface area of the cerebral cortex and form brain division

Deep Sulci

• These divide the cerebrum into lobes, which are named after the overlying skull bones

Central Sulcus

it separates the frontal and parietal lobes

• It’s bordered by two gyri

2 gyri that border the Central Sulcus

• Precentral gyrus

• Postcentral ggyrus

Cerebral Hemispheres Keys Features

• Parieto-occipital sulcus: seperates occipital and parietal lobes

• Lateral Sulcus (Sylvan Fissure): separates temporal from parietal and frontal lobes

• Insula: Deep within the lateral sulcus

5 Lobes of the Cerebral Cortex

1. Frontal Lobe

2. Parietal lobe

3. Occipital lobe

4. Temporal lobe

5. Insular lobes

Frontal Lobe

• Rostral brain

• Involved in motor control, planning, reasoning, and decision making

Parietal Lobe

• Caudal to the frontal lobe

• Involved in sensory processing, spatial awareness and perception

Occipital Lobe

• Caudal brain

• Responsible for visual processing

Temporal Lobe

• Inferior to frontal and parietal lobes

• Involved in auditory processing, memory and language comprehension

Insular Lobe

• Deep within the lateral sulcus

• Plays a role in emotion, self-awareness and taste

Cerebral Cortex

the outermost layer of the brain, responsible for higher cognitive functions, sensory perception, voluntary movement, and decision-making. It is made up of gray matter consisting mainly of neurons, dendrites, and synapses

• has 47 distinct regions which is known as the Brodmann Areas