Subcortical Nuclei, Cerebellum, and Brain stem

What structures make up the basal ganglia? (from superior to inferior)

• Caudate

• Putamen

• Globus pallidus

• Subthalamic nucleus

• Substantia nigra

What is the major function of the basal ganglia?

Important for background muscle tension that allows conscious movement, habit learning

What can happen with basal ganglia dysfunction?

Damage to it can cause extrapyramidal symptoms (movements not started in motor strip)

• Parkinsonian - tremors

• Dyskinesia - unintentional movements

• Dysarthria - slurred speech, weakness

What does the substantia nigra do?

• Produces dopamine

• Projects to the rest of the basal ganglia

• Important for facilitating movement

• “Black substance” - due to neuromalin in dopaminergic cells- when they die, this relates to parkinsons symptoms

How is the substantia nigra related to Parkinson's?

• “Black substance” - due to neuromalin in dopaminergic cells- when they die, this relates to parkinsons symptoms

Subcortical Nuclei

• Limbic System

• Striatum (subsection of basal ganglia): (1) Caudate Nucleus and (2) Putamen

• Lentiform (subsection of basal ganglia): (1) Putamen and (2) Globus Pallidus
  
  

• Basal ganglia (Striatum, Lentiform, Subthalamic nuclei, Substantia nigra)

Limbic System Structures

Hippo HAT:

Hippocampus
Hypothalamus
Amygdala
Thalamus

Hippocampus

Memory

Hypothalamus

organizes limbic system, homeostasis, hormones, behavioral/emotional responses

Amygdala

Emotion

Thalamus (+reticular activating system)

major sensory relay

• the reticular activating system helps arouse/focus the cortex on important sensory stimuli.

• Composes most of the diencephalon

What is the primary function of the cerebellum?

→ Motor control and coordination of skilled movements, including speech.

What is ataxia?

→ Damage here can cause ataxia

→ Lack of coordination.

→ changes in motor speech processes

What might cerebellar damage cause?

→ Unsteady gait, changes in motor speech, difficulty swallowing, nystagmus (concussion sign of eyes wavering back and forth), etc.

Peduncle

large tract of motor/sensory axons connected to the cerebellum

Brainstem ORDER

Midbrain
↓
Pons
↓
Medulla
↓
Spinal cord

What is a general function of the brainstem?

→ Nerves traveling between the body and brain pass through it.

What is the pons associated with in these slides?

→ Unconscious breathing/respiratory control. (pons connects to peduncles to cerebrum and cerebellum)

What is the medulla associated with?

→ Heart rate, blood pressure, vomiting, and some breathing.

Locked-in syndrome

Stroke in basilar artery, affecting pons

• Lesion in the brainstem

Locked-in syndrome is a rare neurological condition where a person is fully conscious and mentally alert, but experiences near-total body paralysis and cannot speak or move.

Diencephalon

1. Thalamus

2. Hypothalamus

3. Pituitary gland

4. optic tract

What are the three meningeal layers, from superficial to deep?

DAP -

Dura mater (hard or tough mother)

Arachnoid mater (spider mother)

Pia Mater (tender mother)

What do the meninges generally do?

Hold cortical structures in place and protect them from damage

What are the two parts/layers of cranial dura mater?

Superficial lamellae → outer layer/periosteum

Meningeal lamellae → actual dura mater

How does Dura relate to the cerebral hemispheres?

Know:

Falx cerebri → separates cerebral hemispheres.

Also know:

Falx cerebelli → associated with separating cerebellar hemispheres.

Tentorium cerebelli → prevents the cerebrum from crushing the cerebellum.

(INSULATES HEMISPHERES)

What is special about the arachnoid?

Fibers connect the arachnoid to the pia, giving it its spider-web-like appearance.

Arachnoid villi protrude through dura to allow CSF to drain into the blood stream

• CSF present iin subarachnoid space

Where is CSF relative to the meninges?

Subarachnoid space

Meaning:

Arachnoid

↓
CSF in subarachnoid space

↓
Pia

CSF helps

• Cushion brain

• Keeps it afloat so it doesn’t weigh itself down

• Provides nutrients

• Waste elimination

Where does CSF exist?

Ventricles + subarachnoid space

What produces CSF?

Choroid plexus in the ventricles (mostly)

What cels make up the choroid plexus?

Ependemal cells

What is the CSF Pathway?

Lateral ventricles

↓

Third ventricle

↓

Cerebral aqueduct

↓

Fourth ventricle

↓

Subarachnoid space

↓
Arachnoid Villi (comes out through arachnoid villi)

Pia Mater

Pia is porous to blood vessels

• Cranial pia mater follows brain surface closely, down into sulci

• Attached to brain surface by astrocytes

• Spinal pia mater also follows nerve tissue closely (thicker than cranial)

• Also secretes CSF (b/w ¼ and 1/3 )

Where do the ACA and MCA begin?

Internal carotid artery - which enters lateral and optic chiasm, branches to become anterior and middle cerebral arteries (MCA+ACA)

What is the pathway of the MCA?

MCA→ travels laterally along inferior surface → enters/runs through Sylvian fissure.

What is the pathway for the ACA?

Corpus callosum → travels upward into the middle fissure of the brain, curves around the anterior and superior surfaces of the corpus callosum, and runs backward along its top surface

• 80% of bloodflow for Corpus Callosum

• Some of the basal ganglia blood

Distal blockages of ACA can cause..

motor aberrations in genitals and legs (incontinence, paralysis) → motor and sensory strip areas along somatotopic map affected

MCA runs along and supplies…

runs laterally along inferior surface of the brain, then through the Sylvian fissure

Supplies lateral surface, including temporal, lateral motor strip, Broca’s, and Wernick'e’s

Occlusions cause global aphasia if proximal, Broca’s or Wernicke’s if distal

• Facial or arm weakness

What it causes when MCA occluded

Occlusions cause global aphasia if proximal, Broca’s or Wernicke’s if distal

• Facial or arm weakness

Where does the PCA begin?

Basilar artery (branches at ventral portion of pons to become PCA)

What do the communicating arteries do?

ACA + MCA:

→ provide cross-connections/anastomoses
→ are part of the Circle of Willis
→ help keep blood pressure equal.

Anastomosis/anastomoses

a cross connection (or connections) between blood vessels

The Circle of Willis provides _____, helping maintain blood flow if there is a blockage

redundancy (to ensure blood flow in case of blockages)