2 Maintaining Homeostasis Homeostasis is the process by which organisms keep internal conditions relatively constant despite changes in external environments.Homeostasis in the body is maintained by feedback inhibition.
3 Maintaining Homeostasis Feedback inhibition (negative feedback) = the process in which a stimulus produces a response that opposes the original stimulus.
4 Maintaining Homeostasis An Example of Feedback InhibitionThermostat senses temperature change and switches off heating systemRoom temperature increasesRoom temperature decreasesHomeostasis is the process by which organisms keep internal conditions relatively constant despite changes in external environments. A home heating system uses a feedback mechanism to maintain a stable, comfortable environment within a house.Thermostat senses temperature change and switches on heating system
5 35.2 The Nervous System An Overview The NS interprets stimuli and coordinates other organ systems to respond to stimuliA nerve impulse, or action potential, is an electrical signal that travels like a wave over the length of a nervous system cell called a neuron
6 Cells of the NS Neurons include: Sensory neurons transmit impulses from the environment to the spinal cord and brainMotor neurons carry instructions from the brain and spinal cord to muscles and glandsInterneurons are the most abundant and transmit signals from one neuron to another
7 Anatomy of a NeuronThe cell body contains the nucleus and other organellesDendrites receive stimuli and conduct impulses towards the cell bodyThe axon carries impulses away from the cell bodyCell BodyDendriteAxon
8 Nodes of Ranvier are the gaps between neighboring Schwann cells Axon TerminalsDirection of impulseNodes of RanvierMyelin SheathThe myelin sheath is composed of cells called Schwann cells and insulate the axonNodes of Ranvier are the gaps between neighboring Schwann cellsAxon terminals are the ends of the axon
9 The SynapseA synapse is the space between a neuron and another cell
10 Neurotransmitters are chemicals that are stored in the axon terminals and released into a synapse when triggered by an impulsesend message to the next neuronAn impulse begins when a neuron is stimulated by another neuron or by the environment.
11 35.3 Divisions of the Nervous System 2 Major Divisions:Central Nervous System (CNS) = the brain and spinal cordPeripheral Nervous System (PNS) = cranial and spinal nerves
12 The CNSThe central nervous system relays messages, processes information, and analyzes information.meninges = the protective membrane covering the brain and spinal cordcerebrospinal fluid (CSF) = fluid that circulates around the CNS and provides cushioningentire CNS encased in bone
13 The Human Brain Cerebrum Thalamus Pineal gland Hypothalamus Cerebellum PonsPituitary glandHypothalamusCerebrumMedulla oblongataSpinal cordCerebellumPineal glandThalamus
14 Adult human brain is composed of ~100 billion neurons The cerebrum is the largest and most prominent region of the human brain.controls the voluntary, or conscious, activities of the bodydivided into right and left hemispheres, which control sensory and motor functions of the opposite side of the body
15 The second largest region of the brain is the cerebellum. coordinates and balances the actions of the muscles so that the body can move gracefully and efficientlyThe brain stem connects the brain and spinal cord.It has two regions: the pons and the medulla oblongata. Each region regulates information flow between the brain and the rest of the body.Blood pressure, heart rate, breathing, and swallowing are controlled in the brain stem.
16 The spinal cord is the main communications link between the brain and the rest of the body. certain information, including some kinds of reflexes, are processed directly in the spinal cord.A reflex is a quick, automatic response to a stimulus.
17 Concept Map The Nervous System Section 35-3 is divided into Central nervous systemPeripheral nervous systemwhich consists ofwhich consists ofSpinal NervesBrainSpinal Cord