are the two divisions of the autonomic nervous system (ANS). They are antagonistic (opposing) effects on the internal organs they innervate thus they are known to have antagonistic control
are involuntary action
positive feedback , negative feedback , or reflex arc .
uterine contraction lead to oxytocin release, which causes more uterine contraction. blood clotting platelets activated at wound site attract more platelet activation and clumping.
drop in blood pressure causes ADH release, which increases it. Conversely increase in blood pressure causes a drop in ADH.
withdrawal from a painful stimulus = negative feedback. knee jerk = tapping the knee tendon causes sudden stretching of the muscle, which lead to contraction of that muscle that creates the knee jerk = negative feedback. receptor → sensory neuron → integration center → motor neuron → effector
site of stimulus
carries impulse from receptor to integration center
connects sensory to motor neuron via synapse inside the CNS
no interneuron, direct synapse of sensory to motor.
Golgi tendon reflex
sudden contraction of the quads (extensor), causes a negative feedback that relaxes the quads and contracts the hamstrings (flexor).
Spinal cord provides
the synapse (or synapses if it's polysynaptic) for the reflex arc.
Even though the reflex arc
bypasses the brain, the brain is still aware of it happening.
Brain can override
spinal reflexes (eg. you don't jerk away from getting a vaccine shot)
touch, heat and pain receptors close to the surface (dermis-epidermis boundary), pressure receptors deeper in the dermis.
senses the position of a body part, located in muscle and connective tissue
temperature change (a warm object will feel warm if your hand is cool, but won't feel warm if your hand is already warm)
pain (extreme heat, cold, pressure, chemicals)
Chemicals enter the nose via nostrils. Gets into the nasal cavity. Trapped in the mucus on top of the nasal cavity. Picked up by the membrane receptors on cilia (non-mobile, but they increase the surface area) of the olfactory receptor cell. Causes cell depolarization, and subsequent transduction of signal to the brain.
Chemicals dissolve in saliva. Carried inside taste bud Hair-like microvilli of taste cells inside taste bud picks up chemicals. Releases neurotransmitters to send signal to brain.
Sound enters ear. Hits ear drum (tympanic membrane) Malleus (hammer) → Incus (anvil) → Stapes (stirrup) Vibrates fluid in Cochlea. Transmits to fluid in Cochlea. Cochlear hair cells excited by vibrations, and sends signal to brain.
Photoreceptor cells located on the back of the retina.
senses light and dark (no color), more sensitive.
senses color, less sensitive.
chemical responsible for light reception = Retinal (chemical) + Opsin (transmembrane protein)
cis-retinal → trans-retinal.
then causes hyperpolarization of photoreceptor cell, which prompts the chain of events that sends signal to the brain.
to brain via a bundle of nerves on the back of the retina (where the blind spot is)
Light first travels through the cornea Through the pupil (hole in the iris muscle) Lens = focuses light on retina. Vitreous humor = fluid. Retina = screen on the back of the eye = contains photorecept
visual image processing
The lens of the eye, just like a convex lens in physics, forms a real image on the retina. Real images are inverted. The brain processes this inverted image to make it seem upright in your mind. The brain combines the two images from each eye to make a 3D image, from which you can judge distance. Another reason for combining the two images from both eyes is that it gets rid of the blind spot in each eye.
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