Nervous System Sci13 Lesson 2-3 (Part 1) PDF

Nervous System Sci13 Lesson 2-3 (part 1) Organization of the NS A. Central Nervous System - consists of the Brain and Spinal cord - integrates information B. Peripheral Nervous System - cranial and spinal nerves that branch off from the spinal cord and extend to all parts of the body - form the c...

Nervous System Sci13 Lesson 2-3 (part 1) Organization of the NS A. Central Nervous System - consists of the Brain and Spinal cord - integrates information B. Peripheral Nervous System - cranial and spinal nerves that branch off from the spinal cord and extend to all parts of the body - form the communication network between the CNS and the body parts CNS: Brain - very complex and very compact - an adult's brain weighs only about 3 pounds - has many folds and grooves that store important information - main parts of the brain are the cerebrum, the brainstem, and the cerebellum CNS: Brain a. Cerebrum - biggest part of the brain - large part of the cerebrum is the cerebral cortex (also known as "gray matter"). - cortex has four areas called lobes that work together to create a person's personality and everything they CNS: Brain a. Cerebrum 1. frontal lobe - involved in complex thinking, like planning, imagining, making decisions, and reasoning - located behind the forehead 2. parietal lobe - processes information about touch, taste, and temperature - behind the frontal lobe CNS: Brain a. Cerebrum 3. temporal lobe - understand sounds and language, recognize objects and faces, and create memories - near the ears 4. occipital lobe - processes light and other visual information from the eyes - letting us know what we're seeing - in the rear part of the brain CNS: Brain a. Cerebrum cerebrum has two halves, called hemispheres - A band of nerve fibers (the corpus callosum) connects the hemisphere in the middle (lets them exchange information) - left hemisphere controls the movements of the right side of the body - right hemisphere of the brain controls the movements of the left side of the body CNS: Brain b. Brainstem - connects the brain and the spinal cord - made up of the pons, the medulla, and the midbrain - work together to control and coordinate the messages going in and out of the brain - also controls many body functions (like breathing, heart rate, blood pressure, swallowing, and digestion) CNS: Brain c. Cerebellum - behind the cerebrum - “little brain" (looks like a small version of the cerebrum) - is responsible for balance, movement, and coordination CNS: Other Structure of the Brain a. thalamus - receives messages about the senses, like vision, hearing, and touch coming from the eyes, ears, and fingers b. hypothalamus - controls the pulse, thirst, appetite, sleep patterns, and other processes that happen automatically c. pituitary gland - makes hormones that control growth, metabolism, water and mineral balance, sexual maturity, and response to stress CNS: Spinal cord - long bundle of nerve tissue - about 18 inches long and 1/2 inch thick (adult) - extends from the lower part of the brainstem down the back - three sections that run the length of the spine 1. cervical spinal cord sends nerves to the face and neck 2. thoracic spinal cord sends nerves to the arms, chest, and abdomen 3. lumbar-sacral spinal cord sends nerves to the lower body - cauda equina is a bunch of nerves look like a horse’s tail — is at the bottom of the spinal cord; send and receive messages to and from the lower limbs and pelvic organs PNS - cranial and spinal nerves that branch off from the spinal cord and extend to all parts of the body - form the communication network between the CNS and the body parts - divided into: afferent (sensory) and efferent division of PNS PNS: Sensory (Afferent) - relays messages to the CNS a. Somatic sensory division - carries signals from muscles, bones, joints, skin, and special; sensory signal - consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves  PNS: Efferent division - relays messages from the CNS to the effectors (muscle, glands) a. Somatic efferent division- carries signals to the skeletal muscles b. Autonomic efferent division - carries signals to smooth muscle, cardiac muscle, and glands Cells of the NS A. Neuron (nerve cell) - basic signaling units of the NS - Basic structure 1. nerve cell body 2. dendrites - receive incoming signals 3. axons - carry outgoing signals B. Glial cells (glia or neuroglia) - supporting cells Neurons: Structural differences  Neurons: Structural differences - one nerve process extending from the cell body - only occur in invertebrates - play a role in the glands and muscles  Neurons: Structural differences - have two extensions from the cell body - neurons for the transmission of senses - found in the retina of the eye, roof of the nasal cavity, and inner ear  Neurons: Structural differences - one projection from the cell body - one extends into the PNS and one that to CNS - afferents that project into the spinal cord from skin and muscle  Neurons: Structural differences - single axon and many dendrites - most common type of neuron - located in the CNS and in the autonomic ganglia - eg. spinal cord neuron, purkenji cell, pyramidal cell Neurons: Functional differences  Neurons: Functional differences - neuron which carries the signal (stimulus) from the effector organs to CNS - activated by sensory input from the environment - innervated by large myelinated axons  5 Classes of Sensory Neuron 1. Mechanoreceptor - relay stimulus via mechanically gated ion channels - external stimuli (touch, pressure, stretching, sound waves, and motion)  5 Classes of Sensory Neuron 1. Mechanoreceptor - four major types of encapsulated mechanoreceptors: Meissner's corpuscles Pacinian corpuscles Merkel's disks Ruffini's corpuscles  5 Classes of Sensory Neuron 2. Chemoreceptor - stimulated by changes in the chemical composition - control different processes including smell, taste, and breathing  5 Classes of Sensory Neuron 2. Chemoreceptor - hair-like cilia trap odorant molecules; - sensory receptors on the cilia are proteins, variations in their amino acid chains make receptors sensitive to different odorants  5 Classes of Sensory Neuron 2. Chemoreceptor - each neuron has only one type of receptor on its cilia specialized to detect specific odorants - Olfactory stimulation is the only sensory information that directly reaches the cerebral cortex  5 Classes of Sensory Neuron 2. Chemoreceptor - rely on gustatory receptors (taste cells) - taste bud is a cluster of gustatory receptors (taste cells) located within the bumps on the tongue called papillae  5 Classes of Sensory Neuron Filiform papillae - located across the tongue - are tactile, providing friction that helps the tongue move substances - no taste cells  5 Classes of Sensory Neuron Fungiform papillae - located anterior two-thirds of the tongue - each contains one to eight taste buds - have receptors for pressure and temperature  5 Classes of Sensory Neuron Circumvallate papillae - contain up to 100 taste buds - form a V near the posterior margin of the tongue - each papillae is surrounded by a groove and contains about 250 taste buds  5 Classes of Sensory Neuron Foliate papillae - leaf-like papillae - located in parallel folds along the edges and toward the back of the tongue - contain about 1,300 taste buds within their folds  5 Classes of Sensory Neuron 2. Chemoreceptor - Each taste bud’s taste cells are replaced every 10 to 14 days - Food molecules (tastants) are dissolved in saliva, and they bind with and stimulate the receptors on the microvilli 1. What about Breathing?  5 Classes of Sensory Neuron 3. Thermoreceptor - free nerve endings on the skin surface - Two distinct thermal sensations (detected by different receptors): a. Cold receptors - located in the stratum basale of the epidermis - attached to myelinated A fibers (few attached to unmyelinated C fibers) - Activated at temperatures between 10 and 40 C (50–105 F)  5 Classes of Sensory Neuron 3. Thermoreceptor b. Warm receptors - located in the dermis - attached to small-diameter unmyelinated C fibers - activated by temperatures between 32 and 48 C (90–118 F)  5 Classes of Sensory Neuron 3. Thermoreceptor - they continue to generate impulses at a lower frequency throughout a prolonged stimulus - Temperatures below 10 C and above 48 C stimulate pain receptors, rather than thermoreceptors, producing painful sensations  5 Classes of Sensory Neuron 4. Nocireceptor - receptors for pain - are nerve endings found in every tissue of the body except the brain - Intense thermal, mechanical, or chemical stimuli can activate nociceptors - fast (w/in 0.1 sec; not felt in deeper tissues of the body)/ slow pain (