part 1-The nervous system (2024 modified).pptx

The Nervous System  The Importance of the Nervous System Response to Change… Adjustments made by electrochemical messages to & from the brain or by chemical messengers (hormones). Vertebrate Nervous System Central Nervous System (CNS) Nerves of the brain & spinal cord. Meninges: a...

The Nervous System  The Importance of the Nervous System Response to Change… Adjustments made by electrochemical messages to & from the brain or by chemical messengers (hormones). Vertebrate Nervous System Central Nervous System (CNS) Nerves of the brain & spinal cord. Meninges: a series of 3 membranes that surround and protect the CNS Peripheral Nervous System (PNS) Nerves between organs & the CNS. Includes somatic & autonomic nerves.  Central nervous system Spinal Cord: It extend from the bottom of the skull and into the base of the brain. It is the vehicle of communication between the brain and the peripheral nervous system. The spinal cord contains a central canal which is filled with cerebrospinal fluid, grey matter and white matter. 1. Cerebrospinal Fluid: Spinal Cord Fills the spaces within the meninges to create a cushion that will provide more protection to the CNS. * Meninges: protective membranes that surround the brain and the spinal cord 2. White Matter Found around the grey matter White matter because it contains Myelinated neurons in the CNS. Contains interneurons running together in bundles known as tracts 3. Grey Matter In the shape of the letter “H” and has grey colour due to the non- myelinated neurons in the CNS that lack myelin. Contains sensory neurons, motor neurons and interneurons. Surrounds the central canal (The central canal represents the adult remainder of the central cavity of the neural tube). * Myelin sheath is a fatty layer that surrounds the axon and it increases the speed at which the impulses travel along the axon. THE MENINGES LAYER Dura Layer: the outermost layer of the meninges. It consists of two layers; one layer attached to the middle arachnoid layer and the outer layer attaches to the skull. It is a strong and a thick membrane layer that acts like a drainage system, where the blood is allowed to leave and the cerebrospinal fluid re-enters the brain. Arachnoid Layer: The Middle avascular (lacks the presence of blood vessels) meninges layer. It is a thin layer and has a spider- web like appearance. The connetive, spider-web like projections attach this layer to the pia layer. Within the two layers runs the cerebrospinal fluid. Pia Layer: The innermost compact layer which adheres tightly to the brain and spinal cord. This layer is vascular layer, meaning it is rich with blood vessels.  Spinal Cord White Matter Tracts Ascending tracts: carry information to the brain Descending tracts: carry information from the brain.  Peripheral Nervous System Somatic Nervous System Controls skeletal muscle, bones & skin. Consciously controlled Autonomic Nervous System Controls internal organs (e.g. heart rate, digestion, respiration rate, diameter of pupil and sexual arousal). Includes sympathetic & parasympathetic nervous system. Not Consciously controlled  Autonomic Nervous System 1. Sympathetic Nervous system: “fight-or-flight” reaction which prepares the body to deal with immediate stress E.g. heart rate and breathing rate increase and blood sugar is released from the liver to provide the energy required to deal with the immediate stress. Diagram on page 394 2. Parasympathetic Nervous System: it works to reverse the effect of the sympathetic nervous system response. It promotes calming of the nerves and return to regular function and enhance digestion. E.g. heart rate and breathing rate decrease Anatomy of a Neuron Neurons Functional units of nervous system. Includes sensory neurons, interneurons & motor neurons. Anatomy of a Neuron  Anatomy of a Neuron Dendrites Receives information. Carries impulses toward cell body. Axon Sends impulses away from the cell body toward other neurons and/or effectors.  Anatomy of a Neuron Myelin Sheath Surrounds & insulates axons. Speeds the rate at which the impulses travel along the axon Formed by Schwann cells which are insulating cells around the axon of a nerve cell. Nodes of Ranvier Spaces between myelin sheath. Nerve impulses “jump” from node to node to speed up rate of transmission. Anatomy of a Neuron  Sensory Neurons Known as afferent (inward) neurons. Sense & relay info (stimuli) from the environment to the CNS.  Motor Neuron Known as efferent (outward) neurons. Relay information to the effectors (muscles, organs, glands).  Interneurons Known as association neurons. In brain & spinal cord. Integrate & interpret sensory stimuli. Connect afferent & efferent neurons. Integration of the Different Neurons  Neural Circuits & Reflexes Reflex Arc Stimulus →receptor → sensory neuron → interneuron (spinal cord) → motor neuron → effector involuntary & unconscious. Reflex Arc The Brain  The Brain The brain is the organizing and processing center of the nervous system. It is the site of consciousness, sensation, memory and coordination. The brain processes the information that is transmitted through the senses so the body can deal with the changes in the external and internal environment.  The Brain The human brain makes up 2 percent of the body weight. It contains 15 percent of the body’s blood supply. It consumes about 20 percent of the body’s oxygen and glucose.  The Brain The brain stem consists of: Medulla oblangata Pons Midbrain  Parts of the brain The Medulla Oblongata Attached to the spinal cord at the base of the brain. Cardiac Centre: it controls heart rate and the force of the heart’s contractions. Vasomotor Centre: it adjusts blood pressure by controlling the diameter of blood vessels. Respiratory Centre: controls the rate and depth of breathing. Also contains reflex centre for vomiting, coughing, hiccupping and swallowing.  Parts of the Brain Pons Contains axons travelling between the cerebellum and the rest of the CNS. Functions with the medulla to regulate breathing rate. Has reflex centre involved in head movement.  Parts of the brain Midbrain A short segment of the brain stem between the cerebrum and pons; mostly involved in sight and hearing.  Parts of the brain The Cerebellum A large mass of white and grey matter, lying posterior to the medulla oblongata. Serves as a coordinating center for motor activities. Controls muscle co-ordination and maintains muscle tone. Plans and programs skilled and fine motor movement. It controls which muscles should contract and which ones should relax during a certain activity.  Parts of the brain Thalamus Relays all sensory signals except for smell signals to the cerebral cortex. Relays signals to the cerebral cortex if the sensation is mild. However, if the sensation is strong, the thalamus relays the signals to the hypothalamus.  Parts of the Brain The Hypothalamus The Homeostatic Control Centre. The main control centre for the Autonomic Nervous System. Enables the body to respond to external threats by sending impulses to various internal organs via the Sympathetic Nervous System. It stimulates the Parasympathetic nerves to re- establish homeostasis.  The Parts of the Brain The Cerebrum The Centre of Human Consciousness.’ Divides into two hemispheres and each hemisphere is divided into four lobes: the Frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe. Contains areas that receive and integrate sensory signals (somatic sensory areas, visual area, auditory area). Contains areas that initiate motor signals for voluntary movements (somatic motor area and speech area). Contains association area where memories are stored and decisions are made. Parts of the Cerebrum: 1. Frontal Lobe: Motor elaboration, Tongue, Swallowing and it is associated with learning, logic, foresight and creativity. 2. Temporal Lobe: Hearing and auditory recollection. 3. Occipital Lobe: Primary visual area. 4. Parietal Lobe: Primary taste area, Salivation, primary somatic sensory area, helps one to understand speech and express thoughts.  Parts of the Brain The cerebral Cortex The thin layer that covers each hemisphere of the brain. It enables us to experience sensation, voluntary movement and all the thought processes we associate with consciousness  Parts of the Brain Ventricles Are cavities within the brain that produce and store cerebrospinal fluid. CSF is produced by the choroid plexus (CF) which a junction of capillaries between the two lateral ventricles that are lined by ependymal cells that help regulate CSF pressure. They provide protection and cushioning to the brain. They regulate intracranial pressure. They help distribute nutrients and remove waste. They consist of three main parts: the lateral ventricle - > the third ventricle -> the fourth ventricle.  Parts of the Brain The Corpus Callosum A layer of white matter made up of axons. Transfers impulses from one hemisphere to the other. The Limbic System It is the Centre of memory, learning, and our behavioral and emotional responses especially those that we need for survival (feeding, reproduction, caring for our young ones, fight or flight responses). The limbic system includes: Hippocampus: Responsible for our long term memory, it also helps us associate memories with various senses. It s also important for spatial orientation (map reader of the brain) and our ability to navigate the world. Amygdala: Two almond shaped structure in the brain located deep within the temporal lobe. It is responsible for our emotional responses such as pleasure, fear, anxiety and anger. It plays a key role in forming new memories related to fear. Hypothalamus: production of important hormones and regulation of thirst, hunger, mood etc. Basal ganglia: reward processing, habit formation, movement and learning. The cingulate gyrus: is the curved fold that covers the corpus callosum. It is responsible for the processing of emotions, and pain. It is also involved in predicting and avoiding negative consequences. It drives the body’s conscious response to avoid negative/unpleasant consequences.  Memory Short-term memory: also called working memory, occurs in the prefrontal cortex. It stores information for about one minute and its capacity is limited to about 7 items. Long-term memory: is processed in the hippocampus of the temporal lobe and is activated when you want to memorize something for a longer time. This memory has unlimited content and duration capacity. It contains personal memories as well as facts and figures. Skill memory: is processed in the cerebellum, which relays information to the basal ganglia which works with the cerebellum to coordinate fine motions. Technologies used to monitor/scan the brain: EEG (electroencephalogram): It measures the electrical activity of the functioning brain and produces a print out that allows doctors to diagnose disorders such as epilepsy and to locate brain tumors. EEG reading are also used to study brain activities during sleep to help diagnose and understand sleeping disorders. CAT (Computerized Tomography) scans: cross- sectional x-rays to create a computer generated, 3D image of a part of the body Technologies used to monitor/scan the brain: PET (Positron Emission Tomography) scans: They identify which areas of the brain are most active when the subject performs certain tasks. MRI (Magnetic Resonance Imaging) scans: use a combination of large magnets, radio frequencies and computers to produce detailed images of the brain and other parts of the body to enhance our knowledge of both healthy and diseased brains.