Transcript NS Review
NS Review Nervous system • Coordinates and regulates the function of all other body systems • 2 major division – Central Nervous System (CNS) • Brain • Spinal Cord – Peripheral Nervous System (PNS) • Nerves – carry sensory info to the CNS – Motor commands from CNS to muscles Neurons 3 types of neurons Sensory neurons Take messages to the CNS Sensory receptors detect changes in the environment Interneuron Receive input from the sensory neurons before communicate to motor neuron Motor neuron Takes message away from CNS to rest of body (organ, muscle or gland) Neurons • Anatomy of a neuron – Cell body – Dendrites • Receive signals from other neurons and send them to cell body – Axon • Conducts nerve impulses away from the cell body and send them toward other neurons Neurons • Myelin Sheath – Formed by Schwann Cells around the axon – Gaps between Schwan Cells are called nodes of Ranvier – Myelin Sheath gives nerves white colour – Helps protect and insulate the nerve – Helps conduct nerve impulse Neurons DIAGRAM Nerve impulse • Nervous system uses a nerve impulse to send information • When an axon is not conducting a nerve impulse we call it at resting potential – More negative inside the axon – Positive outside the axon Nerve impulse Difference in polarity is due to ion concentration More Na+ ions outside the axon More K+ ions inside the axon Sodium-potassium pumps Actively transport Na+ out of axon and K+ into axon 3 Na+ for every 2 K+ Nerve Impulse Action potential Rapid change in polarity across the axon Nerve impulse During an action potential DEPOLARIZATION Sodium channels open up Sodium enters the axon Axon becomes more positive REPOLARIZATION Potassium gates open K+ moves outside of axon Axon returns to original negative charge Synapse • During an action potential the impulse travel along the axon until it reaches the axon terminal • Here gated Ca+ channels open up and Ca+ enters the axon terminal • Synaptic vesicles merge with presynaptic membrane and bind with a specific protein receptors Synapse • Depending on the type of neurotransmitter and receptor the response of the postsynaptic neuron – Excitation • Action potential occurs – Inhibition • Action potential does not occur Types of neurotransmitters • Acetylcholine – triggers muscle contraction – In the central nervous system, it is involved in wakefulness, attentiveness, anger, aggression, sexuality, and thirst • Dopamine – involved in controlling movement and posture – It also modulates mood Types of neurotransmitters • GABA (gamma-aminobutyric acid) – GABA contributes to motor control, vision, and many other cortical function • Norepinephrine – is important for attentiveness, emotions, sleeping, dreaming, and learning – Norepinephrine is also released as a hormone into the blood, where it causes blood vessels to contract and heart rate to increase. Types of neurotransmitters • Serotonin – contributes to various functions, such as regulating body temperature, sleep, mood, appetite, and pain The Central Nervous System • Brain and Spinal Cord make up the CNS • CNS controls many bodily functions – Breathing – Heart rate – Body temperature – Blood pressure – Emotions – Memory – Creativity Functions of Spinal cord • Provides communication between the brain and the peripheral nerves – Sends sensory information to brain – Realays motor impulses from brain to muscles • Center for thousands of arc reflexes – Allow nerves and muscles to respond quickly to dangerous stimuli The Brain • The four major parts of the brain (in order of highest to lowest functioning) – the cerebrum – the diencephalon – the cerebellum – the brain stem The Brain: Major Parts DIAGRAM The Cerebrum The cerebrum is the largest portion of the brain. The cerebrum carries out the higher thought processes required for learning and memory and for language and speech. The Cerebrum • Cerebral Cortex – Think layer of gray matter • Sulci – grooves • Gyrus – folds The Cerebrum • Primary Motor Area – Controls skeletal muscles – Each body part is controlled by a certain section • Primary Somatosensory area – Sensory information from skin and muscles arrives • Processing Centers Wernicke’s Area: understand written and spoken language Broca’s Area: speech muscle control The Diencephalon The hypothalamus is the integrating center that helps maintain homeostasis by regulating hunger, sleep, thirst, body temperature, and water balance. The thalamus integrates sensory input from the visual, auditory, taste, and somatosensory systems. The Cerebellum The cerebellum receives sensory input from the joints, muscles, and other sensory pathways about the present position of body parts. It also receives motor output from the cerebral cortex about where these parts should be located. The cerebellum maintains balance and posture. The Brainstem The brain stem contains: Midbrain: relay station Pons: bundles of axons traveling b/t cerebellum and rest of brain medulla oblongata: contains a number of reflex centers for regulating heartbeat, breathing, and blood pressure. The Brain DIAGRAM The Brain • The brain is divided into 2 cerebral hemispheres – Left hemisphere – Right hemisphere • Hemispheres communicate with each other though a bridge of white matter called corpus callosum The Brain • Brain divided into 4 lobes – Frontal Lobe • reasoning, motor skills, higher level cognition, and expressive language. – Parietal Lobe • Sensory information – Temporal Lobe • Hearing, formation of memories – Occipital lobe • Vision, interpreting vision Lobes of the brain DIAGRAM The Limbic System Limbic System Emotions & higher mental functions Blends primitive emotions (rage, fear, joy, sadness) with high mental functions (reason, memory) The Limbic system • Anatomy – Hippocampus • Involved in storage of long-term memory – Injured cannot form new memories – Amygdala • Allows us to feel certain emotions and to perceive them in other people – This includes fear and the many changes that it causes in the body Memory • Types of memory – Short-term memory • This ability to hold on to a piece of information temporarily in order to complete a task • It holds a small amount of information (typically around 7 items or even less) • readily-available state for a short period of time (typically from 10 to 15 seconds, or sometimes up to a minute). Memory • Long-term memory – anything you remember that happened more than a few minutes ago – Long-term memories can last for just a few days, or for many years Memory – Semantic memory • General knowledge about the world – Names of colours, capital of Canada – Basic facts that have been collected over lifetimes – Episodic memory • recollection of specific events, situations and experiences – Skill memory • Involved in performing skills – Riding bike, playing hockey, using a keyboard • Skills that become automatic or learned RETREIVING MEMORY Retrieval cues are stimuli that help the process of retrieval Associations Priming - recalling a particular word becomes easier if another, related word is recalled first Context People can often remember an event by placing themselves in the same context they were in when the event happened. Mood If people are in the same mood they were in during an event, they may have an easier time recalling the event Cranial Nerves Somatic Nervous System • responsible for carrying motor and sensory information both to and from the CNS • Responsible for all voluntary muscle movements and processing sensory information (hearing, touch, sight) • Made up of nerves that connect to skin, sensory organs and skeletal muscles Autonomic Nervous System • regulates the functions of our internal organs like the heart, stomach and intestines. • We are often unaware of the ANS because it functions involuntary and reflexively • 2 divisions – Sympathetic – Parasympathetic ANS • The ANS is most important in two situations: – In emergencies that cause stress and require us to "fight" or take "flight" (run away) – In non-emergencies that allow us to "rest" and "digest."