BIO 240 1st Edition Lecture 29Outline of Last Lecture I. Anatomy of Spinal Cordi. Tracts – “White matter”ii. Gray Matteriii. RootsOutline of Current LectureI. Peripheral Nervous System A. SynapsesB. ReceptorsCurrent LectureI. Peripheral Nervous System A. Synapses Where two or more neurons meets.1. Polysynaptic Pathways 99.9% of the pathways in our body. Have 3 or more neurons synapsing. 2. Monosynaptic Pathways Where 2 neurons synapse (only one sensory neuron and one motor neuron). Only make up 0.1% of our body’s pathways. Also known as reflexes. For example, Achilles tendon, patellar tendon, gag reflex, and blinking. Much faster because it bypasses the brain by skipping ascending tracts and descending tracts. B. Receptors of the Nervous System***Occur in the brain too – chemoreceptors1. Specialized cells or tissues that respond to internal or external stimuli. The translators or communicators for the nervous system. 2. Categories by stimulia. *Mechanoreceptors Activated by a physical force. b. *Chemoreceptors Activated by chemicals; for example neurotransmitters. c. Photoreceptors Activated by light. Detect light and are only found in the retina of the eye. There are two types of photoreceptors: rods and cones. d. Baroreceptors Activated by pressure. Stimulated by pressure and pressure changes. Monitor blood pressure. Occur in carotids and aorta. e. Thermorecpetors Activate by temperature. Monitor temperature.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.f. Nociceptors Activated by pain. Specific receptor for all types of pain. There are none in the brain. This is why you don’t feel a tumor in the brain until it grows and impedes functions or grows to tissue outside of brain. 3. Mechanoreceptorsa. Meissner’s (Tactile) Corpuscles Occur in the papillary dermis. Detect fine touch.b. Pacinian Corpuscles Occur in the deep dermis and the hypodermis. Are for deep pressure sensations, but only for about 3 seconds. c. Ruffini Endings Occur in the deep dermis and hypodermis and joints. Are for deep continuous pressure. 4. Chemoreceptors Are located in the CNS and PNS. Helps control the ANS using neuro transmitters. a. Cholinergic receptors Stimulated by AcH or mimics of AcH.i. Nicotinic Nicotine mimics AcH. Found in the adrenal glandsii. Muscarinic The mushroom poison muscarine activates these receptors. Found on parasympathetic fibers and sweat glands (which are on sympathetic fibers).b. Adrenergic receptors Stimulated by epinephrine and Norepinephrine.i. Alpha (1 and 2) Found on blood vessels and constrict blood vessels when activated. ii. Beta (1 and 2) Found on heart and bronchioles. 1. Clinical application: Developing drugs that can bind with the receptors. Beta blockers block the beta 1 receptors on the heart. Blocks the attachment of adrenaline to the heart to keep its rhythm more
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