86 ❯ STEP 4. Review the Knowledge You Need to Score High
released into the synapse where they attach to specific receptor sites on membranes of den-
drites of your postsynaptic neurons, like a key fitting into the tumbler of a lock (the lock and
key concept). Some of your synapses are excitatory, the neurotransmitters cause the neuron
on the other side of the synapse to generate an action potential (to fire); other synapses are
inhibitory, reducing or preventing neural impulses. The sum of all excitatory and inhibitory
inputs determines whether your next neuron will fire and at what rate. The constant flow of
these neurochemical impulses gives your behavior its amazing complexity. It regulates your
metabolism, temperature, and respiration. It also enables you to learn, remember, and decide.reflex action
The simplest form of your behavior, called a reflex, involves impulse conduction over a
few (perhaps three) neurons. The path is called a reflex arc. Sensory or afferent neurons
transmit impulses from your sensory receptors to the spinal cord or brain. Interneurons,
located entirely within your brain and spinal cord, intervene between sensory and motor
neurons. Motor or efferent neurons transmit impulses from your sensory or interneurons
to muscle cells that contract or gland cells that secrete. Muscle and gland cells are called
effectors. Examples of your reflexes include your pupillary reflex, knee jerk, sneezing, and
blinking. Neural impulses travel one way along the neuron from dendrites to axons to ter-
minal buttons, and among neurons from the receptor to the effector.The endocrine system
Your endocrine system interacts with your nervous system to regulate your behavior and
body functions. Your endocrine system consists of glands that secrete chemical messengers
called hormones into your blood. The hormones travel to target organs where they bind to
specific receptors. Endocrine glands include the pineal gland, hypothalamus, and pituitary
gland in your brain; the thyroid and parathyroids in your neck; the adrenal glands atop
your kidneys; pancreas near your stomach; and either testes or ovaries.endocrine gland Function
PINeal glaNd Produces melatonin that helps regulate circadian rhythms and
is associated with seasonal affective disorder.
hyPoThalaMuS Produces hormones that stimulate or inhibit secretion of
hormones by the pituitary.
PITuITary glaNd Sometimes called “master gland” because it produces
stimulating hormones that promote secretion by other
glands including:
TSH—thyroid-stimulating hormone
ACTH—adrenocorticotropic hormone stimulates adrenal
cortex
FSH—follicle stimulating hormone stimulates egg or
sperm production
Produces ADH (antidiuretic hormone) to help retain water in
your body and HGH (human growth hormone).
ThyroId glaNd Produces thyroxine, which stimulates and maintains metabolic
activities.
Lack of thyroxine in children can result in mental retardation.
ParaThyroIdS Produce parathyroid hormone that helps maintain the calcium
ion level in blood which is necessary for normal functioning
of neurons.