Nervous System: Anatomy and Physiology PDF

Nervous System Anatomy and Physiology  Overview of Nervous System Central Nervous System: brain and spinal cord Peripheral Nervous System: nerves and ganglia  -Two basic kinds of nerves: Peripheral 1. Spinal nerves:...

Nervous System Anatomy and Physiology  Overview of Nervous System Central Nervous System: brain and spinal cord Peripheral Nervous System: nerves and ganglia  -Two basic kinds of nerves: Peripheral 1. Spinal nerves: nerves that originate from the spinal Nervous System cord (31 pairs of spinal nerves) Nerves: bundles of neuron axons and their coverings, which are 2. Cranial Nerves: nerves that found outside the CNS originate from the brain (12 Ganglia: collections of neuron cell bodies that are found pairs of cranial nerves) outside the CNS  - Afferent: sensory division, Peripheral carries signals from sensory organs to the CNS allowing the Nervous System information to be processed (both outer sensory organs and internal organs) Afferent neurons: transmit action potentials from the sensory organs - Efferent: motor division, sends to the CNS signals FROM the CNS to effector Efferent neurons: transmit action organs (muscles and glands) potentials from CNS to the effector organs  *we have control over the SNS but not the ANS Efferent Division: Autonomic Nervous System: Two Parts: 1. Sympathetic Division: prepares A) Somatic motor nervous system: PNS neurons that transmit action body for increased energy potentials from CNS to skeletal expenditure muscles 2. Parasympathetic Division: B) Autonomic nervous system: PNS regulates resting and neurons that transmit action nutrition-related functions potentials from the CNS to smooth muscles, cardiac muscles and glands Fight or Flight Sympathetic= provides all the necessary changes that would allow the body to to respond with fight or flight (excited, frightened, or angry)  A. Cell body (soma): houses cell Basic Cells in nucleus, mitochondria, and golgi apparatus Nervous System: B. Dendrites: process, usually shorter, brings messages into the 1. Neurons: has 3 main parts= cell body cell body, axons, and C. Axons: process, longer, sends dendrites signals away from cell body  3. Axon Hillock: area that marks the end of the cell body and the beginning of the axon (place where action potential starts) 4. Collateral axons: branch offs from Axons the axon 1. Myelin sheath: fatty wrapping that 4. Presynaptic terminals: axons end helps to speed up the conduction of action potential down the axon here (Schwann cells-PNS, Oligodendrocytes-CNS) 2. Nodes of Ranvier: gaps between myelin sheath  Types of Neurons 1. Unipolar: only one process with cell body suspended (*doesnʼt really have dendrites) [afferent neurons] 2. Bipolar: two processes=one axon and one dendrite that splits into many branches [specialized afferent neurons Ex: eyes] 3. Multipolar: many processes=several dendrites but one axon [motor neurons or association neurons (conducts action potentials from one neuron to another in the CNS)] *only one axon is ever on a neuron allowing the action potential to never be confused And now make a multipolar neuron out of play-doh and label all the parts *use diagram for help! Reflexes  - Reflexes are preprogrammed, Reflex Arc very hard to counteract the reflex/ override - A basic functional unit of the nervous system - Allows the nervous system to analyze information quickly and respond (no brain involvement, only spinal cord)  How do we learn from the reflex action? There is a diverging circuit for allowing the information to relay Reflex Arc learned responses/information to the brain (green on diagram) 1. Sensory information sent from a afferent neuron This allows the brain and the 2. Signal arrives at spinal cord spinal cord to be able to control 3. The association neuron then the areas of the connects the signal to an efferent neuron 4. Efferent neuron sends the signal to the effector Reflex Lab  -Needs steady supply of oxygen and glucose as it uses tons of energy -Needs B vitamins and minerals for ATP production and needs essential fat in order to make myelin The Central Nervous -receives 20% of the bodyʼs blood System supply The Brain Facts: -3 pounds -Full of association neurons -Adult Brain= 100 billion neurons -Can perform 100 computational steps compared to the 1 billion steps it would take a computer  -Two Kinds of Stroke: Brain Issues 1. Ischemic stroke= blood clot *If the neurons do not have blood cutting off blood supply to part of (ischemia) for only a few minutes the brain lysosomes burst and neurons are 2. Hemorrhagic stroke= blood destroyed vessel bursts in the brain (more -If you lose a neuron itʼs gone forever deadly) -The brain uses only glucose (it cannot *When this occurs the blood that is use proteins or fat to make ATP) toxic to the neurons kills them (the -Hypoglycemia= blood glucose level blood brain barrier that keeps the drops so low that brain gets foggy blood separate from the neurons)  *MRIʼs provides images of internal organs Brain Anatomy Gray Matter: collections of neuron cell bodies and their associated neuroglia White Matter: Bundles of parallel axons and their coverings  -Vital Functions: a. Heart rate b. Breathing/ventilation c. Vasomotor area- controls dilation/constriction of blood vessels (controls blood pressure) d. Reflexes: swallowing and vomiting A. Medulla Oblongata (Brain Stem): -site of decussation= the anatomical crossing over of neurons from left to right, the signals from the left side of the brain go to the right side of the body *Cranial nerves do not decussate -Nuclei= control centers for the vital functions (necessary for life) made of groups of gray matter *If there is a blow to the head and the medulla gets pushed through the foramen magnum it can be fatal B. Pons (Brain Stem): superior to the medulla oblongata, means “bridge” which it forms between medulla and upper brain stem -Contains several nuclei that relay messages between the cerebrum and the cerebellum -Contains nuclei that also help with ventilation (help the body made the switch from inhaling to exhaling C. Midbrain(Brain Stem): in the middle between the upper and lower parts of the brain -Contains 4 nuclei: a) Two help control hearing b) Two help control sight *If a stimulus is detected these nuclei cause you to focus on it Functions occurring throughout the brain stem: 1. Reticular formation= several nuclei that are throughout the brain stem, receive information from afferent nerves (mostly from the face) *Reticular activating system (nuclei and connectors)=determin es cycles of sleeping and waking  1. Thalamus: major relay station, -afferent axons synapse with other neurons, a lot of the incoming stimuli are from sensory neurons (especially touch) -also relays action potentials for motor neurons sent from the brain to spinal cord to muscles Diencephalon -regulates mood and body movements-strong emotions like fear “Between brain”, between the and anger brainstem and the cerebrum -major parts include the thalamus and hypothalamus  Diencephalon -acts like a thermostat for controlling body temperature, causes responses to 2. Hypothalamus: tiny temperature like shivering or panting area inferior to thalamus connected to the pituitary gland -regulates the pituitary gland: this gland secretes lots of hormones which regulate metabolism, reproduction, urination, and response to stress  Parts of Cerebrum: 1. Cortex= outer surface, made up of deeply folded gray matter, these folds are called GYRI (increases surface area) the grooves in between are called SULCI -not thick but contains 75% of neuron cell bodies Cerebrum 2. Underneath cortex is white -largest part of the brain matter with interspersed clumps -higher level brain function: of gray (nuclei) interpreting the sensory signals, reasoning, and memory  Cerebellum -control center for subconscious motor functions a)Muscle tone b) equilibrium/balance c) sequencing muscle contractions *If the cerebellum is not functioning properly then a person will lack coordination d)muscle preset (we have a presupposition regarding the amount of muscle is needed to perform certain tasks) e)Dampening (inhibiting movements) Ex: running with arms swinging  Corpus Callosum White matter that forms the connections between the the right and left side of the brain to help it communicate Now let’s look at the cerebrum in more detail!  Lobes: 1. Temporal Lobe: seen from a lateral view, separated by the lateral fissure- hearing and smell, memory and abstract thought 2. Frontal Lobe: Separated by the central sulcus that runs Cerebrum into the lateral fissure- motor -Divided into two hemispheres by the function and smell, mood, LONGITUDINAL FISSURE emotions, foresight, and -The hemispheres are divided into lobes memory that are named for the bones below  4. Parietal Lobe: located posteriorly to the central sulcus and superior to the temporal lobe and anterior to the occipital- receiving all Cerebrum other sensory information (*not smell, 3. Occipital Lobe: located at the back of vision, and hearing) the skull, doesnʼt have a sulcus or fissure touch that helps to distinguish- receives and integrates sensory information  Functional Areas of the Cerebrum *Functional areas of the brain describe what is done in that area of the brain 1. Primary Somatic Sensory Area/ Cortex *area=cortex -receives general sensory input from all over the body -located mostly on a single gyrus known as the postcentral gyrus, posterior to the central sulcus Once the sensory information is received it localizes the sensations that come from a certain part of the body Primary Somatic -this part of the brain has areas that are directly related to every surface on the body Sensory Cortex Determines the meaning of the sensation Example: Poking -This area also catalogs sensations keeping a record so you recognize the sensation and act Somatic Sensory accordingly *Guessing what is inside Association Area a bag just from touch Visual Cortex & Visual Association Area Receives action potentials from optic nerves attached to the eyes and tells shape, color and size of what is seen -Once this information is acquired the action potential passes to the visual association area where the brain will “check the index” and provides the context for what you are seeing Primary Auditory Area and Auditory Association Area Located on temporal lobe, takes in sensory input for sound (volume and pitch) and the signal passes to the auditory association area in order to gain contex, also helps us make sense out of speech -when the auditory association area catalogs a sound as speech the Wernicke’s Area sensory input is sent to this area where speech is then understood Example: Foreign Language learning Taste Area and Taste: interprets taste Olfactory Area Olfactory: Smell  Primary Motor Area/Cortex Location: precentral gyrus (one gyrus) Controls specific areas of the body for basic skeletal movements Ex: making a fist  For fine motor movements the premotor area does the preparatory work, figuring out which action potentials are needed, once the sequence etc. is determined the information is sent to the primary motor cortex Premotor Area  Broca’s Area Aka “motor speech area” -subsection of premotor area that allows a person to formulate the plan in order to make speech happen Process= Wernickeʼs Area figures out what words will convey the meaning you are wanting to get across and the signals are sent to Brocaʼs area which figure out the muscle movements which then signals the primary motor cortex to cause the action potentials for those movements  Large part that enables us to reason and think, to foresee things that will happen (causes and effects), motivation, helps to inhibit impulses *many parts of personality are controlled here [Prefrontal lobotomy was performed in this area to help control violent or disturbed people Prefrontal Area Time to play telephone…. operator!  Protection of the 2. Meninges: layers of tissues that protect the brain Brain a. Dura Mater= attached to the Ventricles =Filled with cerebrospinal periosteum of the skull fluid(CSF): a clear fluid that cushions the b. Arachnoid mater= the tissue brain resembles thick webbing (between -Ventricles are lined with ependymal cells the dura mater and the arachnoid that secrete the spinal fluid mater is the SUBDURAL 1. Skull: all the bones that are fused SPACE-containing fluid that keeps the together to cover the brain tissue moist) c. Pia Mater= tightly bound to the brain,SUBARACHNOID SPACE is between the layers (filled with CSF) *Meningitis=life threatening infection that causes inflammation of the meninges that can cause paralysis, coma, and death  2. Gray Matter: organized into horns, and the gray matter is centrally located within the The Spinal Cord white matter There are: -surrounded by the vertebral column a) Dorsal=sensory neurons synapse (begins at the base of the brain stem (link/communicate) with association neurons & runs til the 2nd lumbar vertebrae) in the horn -31 pairs of spinal nerves b) Ventral= motor neuron cell bodies c) Lateral= cell bodies of autonomic neurons 1. White matter: categorized by dorsal (posterior), lateral (side) and ventral (anterior) columns, the columns are then divided into fasciculi (nerve tracts)=these have the axons that carry action potentials from the brain with the same type of information The Spinal Cord On the sides of the spinal cord= 1.DORSAL ROOT: enters at dorsal horn, transports afferent signals from sensory receptors to the spinal cord, dorsal root ganglion is made up of the cell bodies of the neurons (unipolar-axons run from receptors to spinal cord) 2. VENTRAL ROOT: exits spinal cord at ventral horn carrying the efferent neurons to the effectors, no ganglia because the motor neurons cell bodies are within the gray matter of the spinal cord