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What’s the function??? Nervous systems contain neural cells and glial cells Types of neurons • Sensory neurons • Interneurons • Motor neurons Fig. 28-1b 1 Sensory 2 Sensory neuron Reflex Arc receptor Brain • Simplest example • Does not send message to brain Motor neuron Spinal cord 3 4 Quadriceps muscles Interneuron Nerve Flexor muscles PNS CNS Fig. 28-2 Signal direction Dendrites Cell Body Cell body Layers of myelin sheaths Signal pathway Nucleus Axon Schwann cell Nucleus Schwann cell Myelin sheath Synaptic terminals Neurons work by sending an electrical impulse (action potential) from one end of the neuron (cell body) to the other (synaptic terminal) -works in ONE DIRECTION only Resting Potential There is a difference in the distribution of charges inside the cell compared to outside -inside is negative; outside is positive There is a difference in the concentration of certain ions inside compared to outside outside high concentration of Na+ inside high K+ Animation link Action Potential A stimulus to a neuron causes Na+ gates to open (Na+ rushes into the cell) reversing the charge cell is DEPOLARIZED Charge distribution is reestablished when K+ is allowed to leave the cell Cell is Repolarized Na+/K+ pump reestablishes the ion concentrations (expends the most energy in your body) Sending the message on Signal reaches synaptic terminal causing vesicles containing neurotransmitters to be released into synapse Neurotransmitters diffuse across the synapse and bind to receptors on receiving cell These receptors are also gated channels -may be Na+ effect? -may be K+ effect? 1 Sending neuron Action potential arrives Vesicles Axon of sending neuron Synaptic terminal Synapse 2 Vesicle fuses with plasma membrane 3 Neurotransmitter is released into synaptic cleft Synaptic cleft Receiving neuron 4 Receiving neuron Ion channels Neurotransmitter molecules Neurotransmitter binds to receptor Fig. 28-7a Dendrites Synaptic terminals Inhibitory Excitatory Myelin sheath Receiving cell body Axon Fig. 28-7b Synaptic terminals Acetylcholine motor neurons / muscles Serotonin & dopamine in brain affect sleep/mood Botulinum toxin -inhibits release of acetylcholine Neurotransmitter Receptor Neurotransmitter broken down and released Ions 5 Ion channel opens 6 Ion channel closes Fig. 28-12 Peripheral nervous system Somatic nervous system Autonomic nervous system Sympathetic division Parasympathetic division Enteric division Fig. 28-13 Parasympathetic division Brain Sympathetic division Eye Constricts pupil Dilates pupil Salivary glands Stimulates saliva production Inhibits saliva production Lung Dilates bronchi Constricts bronchi Slows heart Spinal cord Accelerates heart Heart Adrenal gland Liver Stomach Stimulates stomach, pancreas, and intestines Stimulates epinephrine and norepinephrine release Pancreas Stimulates glucose release Inhibits stomach, pancreas, and intestines Intestines Bladder Stimulates urination Promotes erection of genitals Inhibits urination Genitalia Promotes ejaculation and vaginal contractions • Sensory receptors – Specialized cells or neurons that detect stimuli • All senses trigger the same type of action potential • The brain distinguishes the type of stimulus • Perception is the brain’s integration of sensations Copyright © 2009 Pearson Education, Inc. Cerebral hemisphere Midbrain Hindbrain Diencephalon Midbrain Pons Cerebellum Medulla oblongata Forebrain Embryo (one month old) Spinal cord Fetus (three months old) Embryonic Brain Regions Forebrain Brain Structures Present in Adult Cerebrum (cerebral hemispheres; includes cerebral cortex, white matter, basal ganglia) Diencephalon (thalamus, hypothalamus, posterior pituitary, pineal gland) Midbrain Midbrain (part of brainstem) Pons (part of brainstem), cerebellum Hindbrain Medulla oblongata (part of brainstem) Cerebral cortex Cerebrum Forebrain Thalamus Hypothalamus Pituitary gland Midbrain Hindbrain Pons Medulla oblongata Cerebellum Spinal cord Left cerebral hemisphere Corpus callosum Right cerebral hemisphere Basal ganglia Frontal lobe Parietal lobe Frontal association area Speech Taste Somatosensory association area Reading Speech Hearing Smell Auditory association area Visual association area Vision Temporal lobe Occipital lobe The hypothalamus “master controller” influences many hormones • The hypothalamus – Links the endocrine and nervous systems – Receives input from nerves about body conditions – Responds by sending out appropriate nervous or endocrine signals – Uses the pituitary gland to exert master control over the endocrine system Copyright © 2009 Pearson Education, Inc. Brain Hypothalamus Posterior pituitary Anterior pituitary (Bone) Hypothalamus Hormone Neuron cell Posterior pituitary Blood vessel Oxytocin Anterior pituitary ADH Uterine muscles Kidney tubules Mammary glands Neuron cell Blood vessel Releasing hormones from hypothalamus Endocrine cells of the anterior pituitary Pituitary hormones TSH ACTH FSH and LH Prolactin (PRL) Growth hormone (GH) Thyroid Adrenal Testes or Mammary Entire body cortex ovaries glands (in mammals) Endorphins Pain receptors in the brain HORMONES AND HOMEOSTASIS Copyright © 2009 Pearson Education, Inc. Hypothalamus Thyroid hormones -regulate metabolism Inhibition TRH Anterior pituitary TSH Thyroid Thyroid hormones Inhibition • The pancreas secretes two hormones that control blood glucose – Insulin—signals cells to use and liver to store glucose – Glucagon—causes liver to release stored glucose into the blood Copyright © 2009 Pearson Education, Inc. Body cells take up more glucose Insulin 3 2 Beta cells of pancreas stimulated to release insulin into the blood 4 Blood glucose level declines to a set point; stimulus for insulin release diminishes Liver takes up glucose and stores it as glycogen 1 High blood glucose level Stimulus: Rising blood glucose level (e.g., after eating a carbohydrate-rich meal) Glucose level Homeostasis: Normal blood glucose level (about 90 mg/100 mL) Glucose level Stimulus: Declining blood glucose level (e.g., after skipping a meal) 5 Low blood glucose level Blood glucose level rises to set point; stimulus for glucagon release diminishes 6 Alpha cells of pancreas stimulated to release glucagon into the blood 8 Liver breaks down glycogen and releases glucose to the blood 7 Glucagon Insulin Body cells take up more glucose 3 2 Beta cells of pancreas stimulated to release insulin into the blood 4 Liver takes up glucose and stores it as glycogen 1 High blood glucose level Stimulus: Rising blood glucose level (e.g., after eating a carbohydrate-rich meal) Glucose level Homeostasis: Normal blood glucose level (about 90 mg/100 mL) Glucose level Blood glucose level declines to a set point; stimulus for insulin release diminishes Glucose level Homeostasis: Normal blood glucose level (about 90 mg/100 mL) Glucose level Stimulus: Declining blood glucose level (e.g., after skipping a meal) 5 Low blood glucose level Blood glucose level rises to set point; stimulus for glucagon release diminishes 6 Alpha cells of pancreas stimulated to release glucagon into the blood 8 Liver breaks down glycogen and releases glucose to the blood 7 Glucagon Reproductive hormones • Testosterone – Supports sperm formation – Promotes development of secondary sex characteristics • Estrogen – Promotes female secondary sex characteristics • FHS (folicle stimulating hormone) – Stimulates production of eggs and sperm • Progesterone – Promotes growth of the uterine lining