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Homeostasis: The Nervous System (Central Nervous System (The Brain, The…
Homeostasis: The Nervous System
Homeostasis: the body's natural ability to maintain a stable internal environment. Homeostasis happens through all of the body's various systems, but all of the body's systems are controlled by the brain. ex. Maintaining a stable blood-glucose level, maintaining stable body temperature
Feedback systems: describes the change in the body, and is a 'walkthrough' of the sensors, control centres and effectors involed in the feedback system.
Positive Feedback System: A positive feedback loop is when the body experiences a change and enforces that change. ex. contractions when giving birth ; the body enforces that change by adapting to it.
Negative Feedback System: A negative feedback loop is when the body experiences a change and tries to reverse it back to the 'normal' or stable value. ex. sweating when the body's natural temperature increases.
Components of the nervous system:
Central Nervous System
The Brain
The Spinal Cord
Peripheral Nervous System
Sensory Pathways
Motor Pathways
Somatic Nervous System (Under Voluntary Control)
Autonomic Nervous System (Not Under Control/Involuntary)
Sympathetic Nervous System: fight or flight response, norepinephrine
Parasympathetic Nervous System: activated when body is calm and at rest, capable of thinking for itself and makes good decisions
Cells of The Nervous System
Neurons: cells that are the functional units of the nervous system. Neurons cause synapses which allow the brain to function and which allow people and animals to think, have emotions, remember etc.
Synapses: Commonly referred to as 'when neurons fire' These connections between neurons allow for thoughts, memories and feelings to occur.
Structure of Neuron from the cell body to the branching ends of axon:
Cell body + Nucleus + Dendrites --> Axon --> Branching end of axon
The Axon is covered with a myelin sheath. Between fragments of covered axons, there is a gap called the Node of Ranvier.
Glial Cells: cells in the brain that act like glue and act as fillers for the brain. Glial cells clean the neurons' waste and provide support for the brain.
Reflex Arc: Simple connections which explain reflexes. ex. Moving your hand away from a boiling pot of water
Spinal Cord + Interneuron
Sensory Neuron
Pain Receptor (skin)
Boiling pot of water
Motor neuron
Effector (muscle)
Anatomy of The Brain: Cerebellum --> Cerebrum
Cerebellum : walnut-shaped, reflexes, voluntary fine motor skills
Medulla Oblongata: at base of brainstem: maintain homeostasis, heart rate vaosidilation/constriction etc.
The Pons: above medulla, relay centre for neurons
Midbrain: above the pons, processes neurons in eyes, ears and nose, relays audio and video info
Thalamus: at base of forebrain, connects neurons to different parts. Analogy: circuit
Hypothalamus: under thalamus (hypo-), regulates body environment, blood pressure, heart rate, body temp, controls basic drives (hunger, thirst, anger, pleasure)
Cerebrum: largest part of brain, divided into two hemispheres (intellect, memory, consciousness, language, controls sensory neuron information
Resting Membrane Potential: Electric Potential DIfference (voltage) in the brain, for most unstimulated neurons, the resting potential is -70mv
The process of generating a resting membrane potential is called polarization
Electrical charges are moved across the Sodium-Potassium pump and these ions cause electrical charges to take place in the brain, this is how electrochemical signals are processed
Neurotransmitters: Chemical messengers which send messages across the brain. ex. Norepinephrine in a fight or flight (stressful) situation