Biology: Action Potential and Spinal Cord
ckingmotherCoordination by Neural Signaling
26.1 Invertebrates reflect an evolutionary trend toward bilateral symmetry and cephalization * Invertebrate Nervous Organization * In simple animals, such as sponges, the most common observable response is closure of the osculum (central opening) * Hydras (cnidarians) have a nerve net that is composed of neurons * Planarians, (flatworms) have a ladderlike nervous system * In annelids (earthworm), arthropods (crab), and molluscs (squid) the nervous system shows further advances * Cephalization - concentration of ganglia and sensory receptors in a head region * Ganglion (pl. ganglia) - cluster of neurons
Vertebrate Nervous Organization * Cephalization, and bilateral symmetry, results in paired sensory receptors to gather information about environment * Eyes, ears, and olfactory structures * Central nervous system (CNS) * Spinal cord and brain and develops from an embryonic dorsal neural tube * Ascending tracts carry sensory information to the brain, and descending tracts carry motor commands to the neurons in the spinal cord that control the muscles * Vertebrate brain divided into three parts * Hindbrain - most ancient part and regulates motor activity below the level of consciousness * Midbrain - optic lobes are part of the midbrain and was a center for coordinating reflexes involving the eyes and ears * Forebrain - originally dealt mainly with smell. Later, the thalamus evolved to receive sensory input from the midbrain and the hindbrain and to pass it on to cerebrum * Cerebrum integrates sensory and motor input and is particularly associated with higher mental capabilities
26.2 Humans have well-developed central and peripheral nervous systems * Peripheral nervous system (PNS) consists of all the nerves and ganglia that lie outside the CNS * All signals that enter and leave the CNS travel through
26.1 Invertebrates reflect an evolutionary trend toward bilateral symmetry and cephalization * Invertebrate Nervous Organization * In simple animals, such as sponges, the most common observable response is closure of the osculum (central opening) * Hydras (cnidarians) have a nerve net that is composed of neurons * Planarians, (flatworms) have a ladderlike nervous system * In annelids (earthworm), arthropods (crab), and molluscs (squid) the nervous system shows further advances * Cephalization - concentration of ganglia and sensory receptors in a head region * Ganglion (pl. ganglia) - cluster of neurons
Vertebrate Nervous Organization * Cephalization, and bilateral symmetry, results in paired sensory receptors to gather information about environment * Eyes, ears, and olfactory structures * Central nervous system (CNS) * Spinal cord and brain and develops from an embryonic dorsal neural tube * Ascending tracts carry sensory information to the brain, and descending tracts carry motor commands to the neurons in the spinal cord that control the muscles * Vertebrate brain divided into three parts * Hindbrain - most ancient part and regulates motor activity below the level of consciousness * Midbrain - optic lobes are part of the midbrain and was a center for coordinating reflexes involving the eyes and ears * Forebrain - originally dealt mainly with smell. Later, the thalamus evolved to receive sensory input from the midbrain and the hindbrain and to pass it on to cerebrum * Cerebrum integrates sensory and motor input and is particularly associated with higher mental capabilities
26.2 Humans have well-developed central and peripheral nervous systems * Peripheral nervous system (PNS) consists of all the nerves and ganglia that lie outside the CNS * All signals that enter and leave the CNS travel through