Thalamus and Hypothalamus

Thalamus

Sensory relay for all senses except smell

Involved in motor behavior and motivational behavior

Stroke

damage to the thalamus causes sensory deficits and altered motor functions.

Output (Efferents)

primarily excitatory connections (glutamatergic) to various cortical areas and other brain regions. Enable sensory perception, motor planning, and higher cognitive functions

ventral posterolateral nucleus (afferent)

sensory signals arriving from the body, including visual, auditory, tactile, and proprioceptive input, which are processed by the thalamus before reaching the cortex.

From DCML and spinothalamic

lateral geniculate nucleus 

the relay center for visual information, processing signals from the retina before transmitting them to the visual cortex.

medial geniculate nucleus

the relay center for auditory information, processing signals from the inner ear before transmitting them to the auditory cortex.

ventral anterior/ventral lateral nuclei

the relay centers for motor information, receiving inputs from the basal ganglia and cerebellum before sending them to the motor cortex.

ventroposteromedial nucleus 

the relay center for somatosensory and taste information, processing signals from the face and tongue before sending them to the primary sensory cortex.

from DCML and trigeminal nerve

Lesions in VPL

Can cause contralateral sensory loss and thalamic pain syndrome 

Internal capsule

a band of white matter that connects the thalamus to the cortex, carrying motor and sensory signals.

Internal capsule

patient present with contralateral loss of sensation that is equally distributed between the face an body

Internal capsule lesion

patient may present with contralateral loss of movement and UMN (upper motor neuron) signs

Hypothalamus

a small region of the brain that plays a key role in maintaining homeostasis, regulating body temperature, hunger, thirst, sleep, and circadian rhythms.

TANHATS

T - thirst and water balance

A - adenohypophysis control

N - neurohypophysis control

H - hormones and hunger

A - autonomic regulation

T - temperature regulation

S - sexual expression

Homeostasis of hypothalamus 

• Cardio vascular control (HR and BP)

• Regulation of salt and water balance (release of ADH)

• Temperature regulation 

• Energy balance and signaling 

• Coordination of reproductive functions

autonomic responses

receiving sensory input about the internal environment and sending out commands to regulate smooth muscle, cardiac muscle, and glands throughout the body 

Behavioral responses

connection with the limbic system allow the hypothalamus to integrate emotional states and motivational drives with physiological responses, influencing learned behaviors, fear responses, and reward pathways 

Hormonal responses

direct and indirect outputs to the pituitary gland enable the hypothalamus to exert comprehensive control over the endocrine system, regulating the release of wide array of hormones that influence metabolism, growth, stress response, and reproduction

Paraventricular and supraoptic nuclei

• regulate water balance

• produce ADH and oxytocin

• destruction causes diabetes insipidus

Paraventricular nucleus

projects to the autonomic nuclei of brain stem and spinal cord

Anterior nucleus 

• thermal regulation

• stimulate parasympathetic NS

  • destruction results in hyperthermia 

Preoptic area

• contains sexually dimorphic nucleus

• regulates release of gonadotropic hormones

Suprachiasmatic nucleus

• receives input from retina

• controls circadian rhythms

Dorsomedial nucleus

• involved in regulating feeding behavior and autonomic functions.

Posterior nucleus 

• thermal regulation (conservation of heat)

• destruction results in inability to thermoregulate

• stimulate the sympathetic NS

Lateral rectus

• stimulation induces eating

• destruction results in starvation

Mamillary body 

• Receives input from hippocampal formation via fornix

• projects to anterior nucleus of thalamus 

• contains hemorrhagic lesions in Wernicke’s encephalopathy 

Ventromedial nucleus

• satiety center

• destruction results in obesity and savage behavior

Arcuate nucleus

• produces hypothalamic releasing factor

• contains DOPA-ergic neurons that inhibit prolactin release

Pituitary gland 

Master endocrine gland that regulates various hormonal functions in the body. It is divided into anterior and posterior lobes, each producing different hormones that influence growth, metabolism, and reproduction.

Anterior pituitary gland 

produces hormones such as growth hormone, prolactin, and adrenocorticotropic hormone, which are crucial for growth, lactation, and stress response.

Posterior pituitary 

gland releases oxytocin and vasopressin, hormones that regulate lactation and water balance.

pituitary fossa

the pituitary lies within

Dura mater

the pituitary is covered by

Pituitary adenoma 

a benign tumor of the pituitary gland that can cause hormone imbalances.

bitemporal hemianopsia

a visual field loss affecting both temporal fields, often associated with pituitary tumors.

Posterior pituitary

stores and secretes hormones like oxytocin and vasopressin produced in the hypothalamus.

magnocellular neurosecretory cells

neurons located in the hypothalamus that produce and secrete large quantities of hormones such as oxytocin and vasopressin.

oxytocin

a hormone produced in the hypothalamus that regulates social bonding, sexual reproduction, and childbirth.

vasopressin

a hormone produced in the hypothalamus that helps regulate water balance and blood pressure.

Anterior pituitary 

a gland that produces hormones such as growth hormone, prolactin, and adrenocorticotropic hormone, which regulate various physiological processes including growth, metabolism, and stress response.

suprachiasmatic nucleus

a small region in the hypothalamus that regulates circadian rhythms and the sleep-wake cycle.

Posterior Hypothalamic area

sympathetic response, fight/flight, heating

anterior hypothalamic area

a region in the hypothalamus involved in thermoregulation, thirst, and sexual behavior. parasympathetic

ventralmedial nucleus

satiety, off button for hunger

stimulation - aphagia 

lesion - hyperphagia

lateral hypothalamus

hunger, eating behavior, arousal

stimulation - hyperphagia

lesion - aphagia

Supraoptic nucleus and paraventricular nucleus

will produce antidiuretic hormone (ADH) released to anterior pituitary 

anterior hypothalamus

cooling - heating loss

parasympathetic

posterior hypothalamus

heating - heat conservation sympathetic regulation of temperature

SCN

sees light and inhibits melatonin

circadian rhythm

the body's natural cycle of physical, mental, and behavioral changes over a 24-hour period, influenced by light and darkness.