Chapter 37 BIOL1000 Dr. Mohamad H. Termos Nervous System Chapter 37 BIOL1000 Dr. Mohamad H. Termos

Nervous systems/organization Biology, 9th ed, Sylvia Mader Chapter 39 Nervous systems/organization Detect changes in conditions inside and outside the body Elicit responses from muscles and glands Nervous system/tissue/cells are important for: getting food escape predation Mating maintain homeostasis Neurons & Nervous Systems

Nervous System Nerve net: Composed of neurons in contact with one another and with contractile cells in the body wall. Help in swimming movement, keep right side up, capture prey. Ex. Hydra, jellyfish, sea anemone http://www.youtube.com/watch?v=760lUxyle6I Ladder-like nervous system: Ex. Planaria. With primitive senses of smell and sight. True nervous systems: Annelids, Arthropods and Molluscs. Vertebrate nervous systems: more complex and greater ability to integrate information

Biology, 9th ed, Sylvia Mader Chapter 39 Human Nervous System Nervous system has three specific functions Receiving sensory input Assess input and performing integration Generating motor output Neurons & Nervous Systems

Biology, 9th ed, Sylvia Mader Chapter 39 Human Nervous System Central nervous system (CNS) Brain and spinal cord Lies in the body midline The peripheral nervous system (PNS) Nerves and ganglia outside the CNS Gather info from sensors Conduct decisions to effectors Neurons & Nervous Systems

Biology, 9th ed, Sylvia Mader Chapter 39 Nervous Tissue Neuroglia: supportive cells Neurons: excitable cells Cell body contains nucleus Dendrites receive signals Axon conducts nerve impulses Myelin sheath aka nerve fiber Neurons & Nervous Systems

Sensory (afferent) neurons Accept impulses from sensory receptors Transmit them to the CNS Interneurons Convey nerve impulses between various parts of the CNS Motor (efferent) neurons Accept nerve impulses from the CNS Transmit them to muscles or glands

Nervous Tissue: Transmission of Nerve Impulses - Resting Potential: The membrane potential (voltage) when the axon is not conducting an impulse The inside of a neuron is more negative than the outside Due in part to the activity of the sodium-potassium pump Polarized - Action potential - rapid change in polarity across a portion of an axon membrane An action potential is generated only after a stimulus larger than the threshold Gated channel proteins One channel protein suddenly allows sodium to enter the cell Another channel protein allows potassium to leave the cell

Resting and Action Potential of the Axonal Membrane Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. +60 +40 Na+ moves to inside axon K+ moves to outside axon action potential +20 repolarization depolarization Voltage (mV) –20 –40 threshold –60 resting potential 1 2 3 4 5 6 Time (milliseconds) 9 d. An action potential can be visualized if voltage changes are graphed over time.

Nervous Tissue Propagation of Action Potentials In nonmyelinated axons, the action potential travels down an axon one small section at a time In myelinated fibers, an action potential at one node causes an action potential at the next node Saltatory (jumping) Conduction

Nervous Tissue Conduction of a nerve impulse is an all-or-nothing event Intensity of signal is determined by how many impulses are generated within a given time span

Nervous Tissue Transmission Across a Synapse Synapse- Synaptic cleft Neurotransmitters Increase in Ca Vesicles to merge with the membrane Neurotransmitter molecules are released into the synaptic cleft

The Central Nervous System Consists of the brain and spinal cord Meninges - Three specific functions: Receives sensory input Performs integration Generates motor output

The Central Nervous System Spinal Cord Functions Center for many reflex actions Communication between the brain and spinal nerves Composed of grey matter and white matter Cell bodies and short unmyelinated fibers Myelinated long fibers of interneurons running in tracts give white mater its color

Biology, 9th ed, Sylvia Mader Chapter 39 Human Brain Function: Receives, integrates, stores and retrieves information and coordinates responses Neurons & Nervous Systems

The Human Brain Cerebrum (telencephalon) opening to lateral ventricle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cerebrum (telencephalon) opening to lateral ventricle third ventricle skull Diencephalon thalamus (surrounds the third ventricle) meninges corpus callosum hypothalamus pineal gland pituitary gland fourth ventricle Brain stem midbrain Cerebellum pons medulla oblongata spinal cord a. Parts of brain b. Cerebral hemispheres

The Central Nervous System Cerebrum is the largest portion of the brain in humans Communicates with, and coordinates the activities of, the other parts of the brain Higher thought processes Left and right cerebral hemispheres

The Central Nervous System Cerebral Cortex A thin and highly convoluted outer layer of gray matter Covers the cerebral hemispheres Contains motor areas and sensory areas as well as association areas

Biology, 9th ed, Sylvia Mader Chapter 39 Lobes of Cerebrum Frontal lobe – motor control, memory, reason Parietal lobe – sense impulses from skin, muscles, and sense of taste Occipital lobe- vision Temporal lobe- hearing Neurons & Nervous Systems

The Central Nervous System Basal nuclei Integrate motor commands Ensures that the proper muscle groups are either activated or inhibited

The CNS: Diencephalon Includes three structures: - Hypothalamus Integrating center that maintains homeostasis Controls the pituitary gland - Thalamus Receives all sensory input except smell Integrates sensory information and sends it to the cerebrum - Pineal gland Secretes melatonin

The CNS: Cerebellum Receives sensory input from the eyes, ears, joints, and muscles Sends motor impulses out the brain stem to the skeletal muscles Maintains posture and balance and coordinates movements

The CNS: Brain Stem Midbrain Relay station for tracts passing between the cerebrum and the spinal cord or cerebellum Pons Contains axons that form a bridge between the cerebellum and the rest of the central nervous system Medulla Oblongata Contains reflex centers for vomiting, coughing, sneezing, hiccupping, and swallowing

The CNS: Limbic System Complex network of tracts and “nuclei” Incorporates the cerebral lobes, the basal nuclei, and the diencephalon Integrates higher mental functions and primitive emotions Important structures in the limbic system are the hippocampus and the amygdala

The CNS: Learning and Memory Memory: The ability to hold a thought in mind or recall events from the past Learning: Takes place when we retain and use past memories Short term memory is associated with the prefrontal area of the frontal lobe Long term memory is associated with the hippocampus

The Peripheral Nervous System Somatic system Includes cranial nerves and spinal nerves Gather information from sensors and conduct decisions to effectors Controls the skeletal muscles Voluntary

The Peripheral Nervous System Reflex Arc Sensory receptors  dorsal root ganglia  spinal cord  Internuerons  motor axons  effector

The Peripheral Nervous System Autonomic system Controls the smooth muscles, cardiac muscles, and glands Innervates all internal organs Usually involuntary Divided into two divisions Sympathetic division Parasympathetic division

The Peripheral Nervous System Sympathetic division Especially important during fight or flight responses Accelerates heartbeat and dilates bronchi Parasympathetic division Promotes all internal responses associated with a relaxed state Promotes digestion and retards heartbeat

Autonomic System Structure and Function Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. inhibits tears stimulates tears constricts pupils dilates pupils ganglion inhibits salivation Sympathetic Division stimulates salivation Parasympathetic Division cranial nerves slows heart speeds heart dilates air passages constricts bronchioles vagus nerve cervical nerves stimulates liver to release glucose stimulates gallbladder to release bile stimulates adrenal secretion increases activity of stomach and pancreas thoracic nerves inhibits activity of kidneys, stomach, and pancreas increases intestinal activity decreases intestinal activity lumbar nerves inhibits urination ganglion stimulates urination sacral nerves causes orgasmic contractions causes erection of genitals sympathetic ganglia Acetylcholine is neurotransmitter. Norepinephrine is neurotransmitter.

Comparison of Somatic Motor and Autonomic Motor Pathways