Basal ganglia, dencephalon and limbic system Presentation

Corpus striatum

basal ganglia and internal capsule

Basal ganglia

caudate nucleus and the lenticular nucleus

(The largest subcortical structure of grey matter in the brain is located near the thalamus)

Lenticular nucleus

putamen and the globus pallidus

The caudate nucleus is divided into

a head, body and tail.

Inhibitory

Amygdala

involved in emotion and is part of the limbic system, is attached to the tail of the caudate nucleus

Ganglia

nerve cell bodies

The internal capsule lies between

the lenticular and caudate nuclei

The internal capsule

is a group of myelinated fiber tracts that connect the cortex to the cell bodies of lower motor neurons

bottleneck of fibers

Because so many axons are clustered within the

internal capsule it is sometimes referred to as

a

• This makes it a very bad place to

get a lesion.

Dopamine

A neurotransmitter that regulates mood and movement, produced in the substantia nigra of the midbrain (brainstem) is sent through the straitum (basal ganglia and internal capsule).

• Dopamine helps humans to have smooth, coordinated muscle movement

Functions of the Basal Ganglia

caudate, putamen, globus pallidus

Stereotypic movements

movements that do not have to be learned on a conscious level

Automated movements

movements that are initially learned and then mediated by the basal ganglia

Tone

the internal state of muscle fiber tension within individual muscles and muscle groups

Dyskinesia

movement disorder

Basal ganglia lesions and associated disorders

• Huntington's chorea

• Tourette's syndrome

• Parkinson's

Huntington's chorea

a progressive degenerative condition of dominant inheritance characterized by involuntary movements, cognitive deficits, and dysarthric speech. Onset at 40-50 years old

• Progressive breakdown (degeneration) of nerve cells in the brain. Huntington's disease has a broad impact on a person's functional abilities and usually results in movement, thinking (cognitive), and psychiatric disorders.

• Medications are available to help manage the symptoms of Huntington's disease, but treatments can't prevent the physical, mental, and behavioral decline associated with the condition

chorea

jerky movement

hyperkinesia

movement disorder

Tourette's syndrome

is a neurological disorder characterized by repetitive, stereotyped, involuntary movements and vocalizations called tics

Parkinson's

degeneration of the substantia nigra and ↓dopamine

Presenting symptoms:

• tremor(pill roll)

• increased tone (cogwheel rigidity, clasp knife)

• decreased coordination of movement

• bradykinesia

• shuffling gait

When approximately 60 to 80% of the dopamine-producing cells are damaged and do not produce enough dopamine, the motor symptoms of Parkinson’s disease appear. This process of impairment of brain cells is called neurodegeneration.

Sinemet

bradykinesia

slowness of voluntary movement

(mask face, poverty of movement)

Septum pellucidum

a membrane separating the anterior horns of the left and right lateral ventricles of the brain

Fornix

a bundle of nerve fibers in the brain that carries efferent tracts from the hippocampus. The fornix also carries some afferent fibers to the hippocampus from structures in the diencephalon and basal forebrain

Diencephalon

thalamus, hypothalamus, epithalamus,

pituitary, and subthalamus

Thalamus

Located in the center of the brain at the level of the temporal lobe.

2 lobes of thalamus separated by the 3rd ventricle

Connected by thalamic adhesion

Hypothalamus

is a solid structure that is located immediately inferior to the thalamus. Part of it is also anterior to the thalamus. It forms the floor and part of the lateral walls of the third ventricle

• Works via the pituitary gland.

• Temperature, thirst and hunger regulation

• Circadian rhythms: Sleep

• emotions

• regulates growth

• Reproduction

• metabolic process

Epithalamus

includes the pineal gland and produces melatonin (sleep cycles)

Subthalamus

located inferior to the thalamus and is important for motor movement. It has connections to the basal ganglia, thalamus, and brainstem

Pituitary gland

works along with the hypothalamus and

secretes hormones controlling growth, reproduction, and metabolic functions

The thalamus receives information from the?

the cerebellum, the basal ganglia and from all sensory pathways with the exception of the olfactory tract; it integrates the messages and sends them on to the cortex for further processing

26

the thalamus has how many pairs of nuclei?

Lateral geniculate nucleus

Visual

Medial geniculate nucleus

Auditory

Ventrolateral geniculate nucleus

primary motor

Ventral Posterolateral Nucleus

primary sensory

Limbic system consists of

• Sensory cortex

• Cingulate cortex

• Hippocampus

• Hypothalamus

• Thalamus

• amygdala

• Mammillary body

• Olfactory bulb

• Prefrontal cortex

The limbic system is involved in

recent memory, emotion, motivation, and reinforcement. Responses mediated by the limbic system include pleasure, satiety, guilt, punishment, inhibition, wakefulness, alertness, excitement, and autonomic activity

prefrontal cortex

The limbic system is tightly connected to the

limbic system

he cortex inhibits the activity of the

Amygdala (almond)

Involved in signaling the cortex of motivationally significant stimuli such as those related to reward, fear, anxiety in addition to social functions such as mating. Plays a role in interpretation of feelings

Hippocampus

Required for the formation of long-term memories

Cingulate gyrus

anxiety and panic and compulsion

Mammillary body

Important for the formation of memory

Olfactory bulb

Olfactory sensory input, memories and smell

Prefrontal cortex

Required for decision making

Behavioral

motivation, fear, aggression, sexual behavior

memory and emotion

Damage specifically to the hippocampus can affect

Lesions in limbic system

• Behavioral: motivation, fear, aggression, sexual behavior

• Damage specifically to the hippocampus can affect memory and emotion.

• Difficulty regulating and interpreting emotions

• *effects of Drugs and alcohol: limbic behavior

• *Alzheimer's-amygdala (fear, anxiety)

• PTSD

• Autism... potential link