HYPOTHALAMUS AND ANS

Flashcards reviewing the hypothalamus and autonomic nervous system.

Hypothalamus

A neural structure lying below the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion and reward.

Hypothalamic Sulcus

A structure forming the boundaries of the hypothalamus.

Hypothalamus Structures

Includes the Mamillary Body, Tuber Cinereum, Neurohypophysis, Anterior Commissure, Third Ventricle, Lamina Terminalis, Median Eminence, Infundibulum Process, Optic Chiasma, Pars Tuberalis, and Adenohypophysis.

Hypothalamus Zones

Preoptic, Suprachiasmatic (Supraoptic), Tuberal, and Mammillary regions.

Anterior Hypothalamic Nucleus

Body temperature, thermal regulation (heat dissipation), stimulates parasympathetic NS; destruction results in hyperthermia.

Medial Preoptic Nucleus

Larger in males; eating, movement, sexual arousal; gonadotropic releasing hormone.

Supraoptic Nucleus

Axon release ADH to posterior lobe of pituitary gland; stimulate by stress, pain, nicotine, morphine; inhibit by alcohol.

Ventromedial Hypothalamic Nucleus

Satiety center; pathology leads to obesity.

Lateral Hypothalamus

Arousal, feeding, reward.

Anterior Hypothalamic Nucleus Function

Thermoregulation, defensive behavior.

Paraventricular Nucleus

Stress response, thyroid regulation, osmoregulation, food intake.

Posterior Hypothalamus

Stress response, blood pressure.

Ventromedial Hypothalamic Nucleus

Water balance control; sense osmotic pressure; drinking center.

Brain

Receives and processes sensory information, initiates responses, stores memories, generates thoughts and emotions.

Spinal Cord

Conducts signals to and from the brain, controls reflex activities.

Motor Neurons

CNS to muscles and glands.

Sensory Neurons

Sensory organs to CNS.

Autonomic Nervous System

Controls involuntary responses.

Sympathetic Division

"Fight or Flight".

Parasympathetic Division

"Rest or Digest".

The Autonomic Nervous System (ANS)

Innervates smooth muscles, cardiac muscle, glands.

Parts of the Autonomic Nervous System (ANS)

Sympathetic and parasympathetic nervous systems.

Autonomic Nervous System

Regulates unconscious body functions to maintain homeostasis.

Sympathetic Nervous System Functions

Dilation of pupils of the eyes and bronchioles of lungs; increases heart rate, blood glucose concentration, blood to skeletal muscles; slows peristaltic action; decreases glandular secretions, blood to digestive organs; relaxes muscles of gallbladder and urinary bladder.

Parasympathetic Nervous System Functions

Constricts pupils of the eyes and bronchioles of lungs; decreases heart rate, blood glucose concentration, blood to skeletal muscles; increases peristaltic action, glandular secretions, blood to digestive organs; contracts muscles of gallbladder and urinary bladder.

Organs Supplied by ANS

Smooth muscles of skin, digestive system, urinary system, respiratory system, walls of blood vessels.

Smooth Muscles of the Eyes

Ciliary muscles, Sphincter pupillae, Dilator pupillae, Tarsal muscles, Orbitalis (muller’s) muscles.

Sphincter Pupillae Muscle

Contracting this muscle decreases pupil size.

Dilator Pupillae Muscle

Contracting this muscle increases pupil size.

Glands Supplied by ANS

Salivary glands & minor glands, lacrimal glands, sweat glands.

Origin of the Sympathetic Nervous System

Intermediolateral cell columns in the lat. horn of spinal cord segments T₁ - L₂ or L₃.

Action of Sympathetic System

One pregang. sym. fiber synapses with numerous postgang. sym. neurons (> 30 ); postgang. sym. fiber synapses with numerous effector cells.

Origin of the Parasympathetic Nervous System

Preganglionic neuron located in the nuclei of the cranial n. III, VII, IX & X and in the intermediolateral cell columns of spinal segments s₂ - s₄.

Parasympathetic Ganglia in the Head

Ciliary, pterygopalatine (sphenopalatine), submandibular, otic ganglion.

Sympathetic Nerve Supply of the Head & Neck

Arise from upper segment of spinal cord -> ventral root -> white rami communicantes -> stellate or inferior cervical ganglion -> ascend to superior cervical ganglion, synapse with postganglionic neurons.

Parasympathetic Nerve Supply of the Head

Preganglionic fibers synapse with postganglionic neurons in 4 parasympathetic ganglia in the head: ciliary ganglion, pterygopalatine (sphenopalatine) ganglion, submandibular ganglion, otic ganglion.

Horner’s syndrome

Constriction of the pupil (miosis), slight drooping of the eyelid (ptosis), vasodilation of skin arterioles, loss of sweating (anhydrosis), enophthalmos (retraction of the eyeball).

Frey syndrome

Patient eats, beads of perspiration appear on the skin covering the parotid; auriculotemporal and great auricular nerves are damaged; stimulus intended for saliva production produces sweat secretion instead.