biomed

Endocrine system function

Slower control than nervous system, releases hormones into the bloodstream from various glands

Processes controlled by endocrine system

Reproduction, growth, maintaining homeostasis, regulating metabolism, and mobilizing body defenses

Hormones

Chemical messengers produced in glands that regulate the activities of other cells throughout the body

Hormone types

Amino-acid based, steroids, prostaglandins

Target cells

Cells with specific receptors for certain hormones

Hormonal responses

1) direct gene activation (turn different genes off/on, steroid based)

2) 2nd messenger systems (wave of cell responses)

Stimuli for hormonal release

1) hormonal: activated by other hormones (most common)

2) humoral: changing blood levels of ions/nutrients

3) neural: nerve fibers stimulate hormone release

Major endocrine organs

Pituitary, pineal, thyroid, parathyroid, thymus, adrenals, pancreas, and gonads

Pituitary gland

At the base of the hypothalamus, controls most of the hormone release, made up of anterior pituitary (growth hormone) and posterior pituitary (oxytocin and vasopressin)

Pineal gland

Hangs from roof of third brain ventricle, secretes melatonin

Thyroid gland

At the base of the throat, regulates metabolism (thyroid hormone) and calcium (calcitonin, decreases blood calcium levels)

Parathyroid gland

Posterior to the thyroid, secretes parathyroid hormone (increases blood calcium levels)

Thymus

Located below the sternum, produces thymosin (matures some white blood cells and helps develop immune system), most active in infants and children

Adrenal glands

Sit on top of kidneys, made up of adrenal cortex (produces corticosteroids, slower stress response), and adrenal medulla (produces epinephrine and non-epinephrine, faster stress response)

Pancreas

Located behind the stomach, produces insulin (decreases blood sugar levels) and glucagon (increases blood sugar levels)

Gonads

Produce sex cells and hormones, found in ovaries (produces corticosteroids estrogen and progesterone) and testes (produce androgen and testosterone)

Brain Lobes

Frontal, parietal, occipital, temporal (one in each hemisphere)

Cerebellum

Coordinates movement: motor learning, stance, limb movements, balance and eye movements

Ataxia

Disorder of the cerebellum, causes uncoordinated movement

Meninges

Protective membranes covering the brain and spinal cord, made up of durable mater (stuck to underside of skull), arachnoid (web-like middle layer), and pia mater (sticks to every gyrus and sulcus of actual brain)

Gyrus

Ridge on the brain’s surface

Sulcus

Groove in the brain’s surface

epidural hematoma

Bleeding between the skull and dura mater, dura starts to peel away

Subdural hematoma

Bleeding directly into brain (dangerous due to toxic pH), bleeding is crescent shaped

Concussions

Brain injury due to a blow to the head causing the brain to move back and forth within the skull, causing the brain to stretch

Ventricular system

holds cerebrospinal fluid (allows brain to float), made up of 4 ventricles, 2 lateral 3rd and 4th

Spinal cord

Nerves that run up and down the length of the back and transmit most messages between the body and brain

Dermatomes

Area of skin that receives sensory input from one spinal nerve root

Reflexes

An automatic response to stimuli that doesn’t require brain involvement

Peripheral nervous system

All nerves that aren’t part of the brain or spinal cord, connects the central nervous system to the rest of the body, divided into somatic and autonomic nervous system

Somatic nervous system

Controls voluntary movement of skeletal muscles

Autonomic nervous system

Controls involuntary bodily functions (ie breathing, digestion), made up of parasympathetic and sympathetic nervous systems

Parasympathetic nervous system

Conserves energy and maintains normal body functions, “rest and digest”

Sympathetic nervous system

Activated during stress or danger, “fight or flight” response

Neurological exam

1) mental status: brain function and cognition

2) cranial nerves: tests for each of the 12 cranial nerves

3) motor exam: muscle strength and control

4) reflexes: spinal cord pathways

5) coordination and gait: balance and movement control

6) sensory exam: ability to feel stimuli

Methods of studying neuroanatomy

Lesion studies: test how removal of a certain part of the brain impacts behavior

Electroencephalogram: identifies timing of events (ie sleep stages)

Neuroimaging: identifies location of events, done through CT, PET, MRI, and fMRI scans

Brain stem

Contains medulla, pons, and reticular formation beneath the thalamus, maintains life support functions (ie heart rate, breathing)

Thalamus

Sensory control center

Limbic system

Helps with emotional regulation and hormonal control, contains amygdala (fear and aggression), hippocampus (memory), and hypothalamus (stress response)

Cortex

Wrinkly exterior of brain, contains white (myelinated axons → tracts/nerves) and gray (neuron cell bodies) matter, as well as glial cells (support cells), and motor cortex is pre-central gyrus, sensory cortex is post centra