Homeostasis 3: The Central Nervous System And The Peripheral Nervous System The Central Nervous System And The Peripheral Nervous System

What’s the Matter?  Grey Matter: is grey because it contains mainly unmyelinated axons, cell bodies, dendrites. It is found around the outside areas of the brain and forms the H-shaped core of the spinal cord.  White matter: contains myelinated axons that run together in tracts. Forms the inner region of the brain and outer region of the spinal cord.  Grey Matter: is grey because it contains mainly unmyelinated axons, cell bodies, dendrites. It is found around the outside areas of the brain and forms the H-shaped core of the spinal cord.  White matter: contains myelinated axons that run together in tracts. Forms the inner region of the brain and outer region of the spinal cord.

The Spinal Cord  Vital communication link between the brain and the peripheral nervous system.  Sensory nerves carry messages from the body to the brain for interpretation  Motor nerves relay messages from the brain to the effectors.  The spinal cord has a ventral side and a dorsal side, white matter and grey matter.  The tissues are protected by cerebrospinal fluid, soft tissue layers and the spinal column.  Vital communication link between the brain and the peripheral nervous system.  Sensory nerves carry messages from the body to the brain for interpretation  Motor nerves relay messages from the brain to the effectors.  The spinal cord has a ventral side and a dorsal side, white matter and grey matter.  The tissues are protected by cerebrospinal fluid, soft tissue layers and the spinal column.

The Brain  The brain can be subdivided into three general regions: the hindbrain, midbrain and forebrain.  The skull protects the brain as well as the meninges.  Three layers of tough, elastic tissue within the skull and spinal column.  The brain can be subdivided into three general regions: the hindbrain, midbrain and forebrain.  The skull protects the brain as well as the meninges.  Three layers of tough, elastic tissue within the skull and spinal column.

Hindbrain  Controls coordination and homeostasis  Cerebellum: involved in unconscious coordination of posture, reflexes, body movements as well as fine voluntary motor skills and receives info from proprioceptors in muscles and joints.  Medulla Oblongata:coordinates many reflexes and automatic body functions such as heart rate, blood vessel size, rate of breathing, swallowing and coughing.  Pons: relay centre between right and left halves of brain.  Controls coordination and homeostasis  Cerebellum: involved in unconscious coordination of posture, reflexes, body movements as well as fine voluntary motor skills and receives info from proprioceptors in muscles and joints.  Medulla Oblongata:coordinates many reflexes and automatic body functions such as heart rate, blood vessel size, rate of breathing, swallowing and coughing.  Pons: relay centre between right and left halves of brain.

Midbrain  Processes sensory input.  The Midbrain takes in information from the eyes, ears and nose and relays info between areas of the hindbrain and forebrain  Controls eye movement and skeletal muscles.  Processes sensory input.  The Midbrain takes in information from the eyes, ears and nose and relays info between areas of the hindbrain and forebrain  Controls eye movement and skeletal muscles.

The Forebrain  Thalamus: provides connections from different parts of the brain, acts as a relay station between forebrain and hindbrain, sensory and cerebellum  Hypothalamus: regulates body’s internal environment and some aspects of behaviour. Controls blood pressure, heart rate, body temp, thirst, hunger, emotions. Also links the nervous and endocrine systems  Cerebrum: largest part. Contains centres for intellect, learning, memory, consciousness, language.  Thalamus: provides connections from different parts of the brain, acts as a relay station between forebrain and hindbrain, sensory and cerebellum  Hypothalamus: regulates body’s internal environment and some aspects of behaviour. Controls blood pressure, heart rate, body temp, thirst, hunger, emotions. Also links the nervous and endocrine systems  Cerebrum: largest part. Contains centres for intellect, learning, memory, consciousness, language.

The Blood-Brain Barrier  The meninges protect the CNS by preventing direct circulation of blood through the cells of the brain and spinal cord.  Blood supply to the brain are made up of tightly fused epithelial cells and large amounts of glial cells called astrocytes surround the capillaries.  Oxygen and glucose can pass through easily. Other lipid-soluble substances such as caffeine, nicotine and alcohol can pass through to the brain directly as well, which explains their rapid effects on brain function.  This protects the brain from toxins and infectious agents.  The meninges protect the CNS by preventing direct circulation of blood through the cells of the brain and spinal cord.  Blood supply to the brain are made up of tightly fused epithelial cells and large amounts of glial cells called astrocytes surround the capillaries.  Oxygen and glucose can pass through easily. Other lipid-soluble substances such as caffeine, nicotine and alcohol can pass through to the brain directly as well, which explains their rapid effects on brain function.  This protects the brain from toxins and infectious agents.

Cerebrospinal Fluid  Within the spaces of the brain and spinal column is a fluid called the cerebrospinal fluid.  It moves hormones, white blood cells, and nutrients across the blood-brain barrier.  Cerebrospinal fluid also acts as a cushion to the brain as it circulates between two layers of the meninges, the arachnoid and pia mater.  Within the spaces of the brain and spinal column is a fluid called the cerebrospinal fluid.  It moves hormones, white blood cells, and nutrients across the blood-brain barrier.  Cerebrospinal fluid also acts as a cushion to the brain as it circulates between two layers of the meninges, the arachnoid and pia mater.

The Cerebrum  The cerebral cortex is responsible for language, memory, personality, vision, conscious thought and more.  It is folded in order to increase surface area.  The right and left halves are known as the hemispheres and are joined by a bundle of white matter called the corpus collosum.  In general the right-brain is associated with holistic and intuitive thinking, visual-spatial skills, and artistic abilities. The left-brain is linked to segmental, sequential, and logical ways of thinking and to linguistic and mathematical skills.  The cerebral cortex is responsible for language, memory, personality, vision, conscious thought and more.  It is folded in order to increase surface area.  The right and left halves are known as the hemispheres and are joined by a bundle of white matter called the corpus collosum.  In general the right-brain is associated with holistic and intuitive thinking, visual-spatial skills, and artistic abilities. The left-brain is linked to segmental, sequential, and logical ways of thinking and to linguistic and mathematical skills.

The Cerebral Cortex  Can be divided into four pairs of lobes.  Occipital Lobe: receives and analyses visual information.  Temporal Lobe: help with the processing of visual information, but mainly their function is auditory reception. Linked to understanding speech and retrieving visual and verbal memories  Parietal Lobe: receive and process sensory information from the skin. Help to process information on the body’s position and orientation.  Can be divided into four pairs of lobes.  Occipital Lobe: receives and analyses visual information.  Temporal Lobe: help with the processing of visual information, but mainly their function is auditory reception. Linked to understanding speech and retrieving visual and verbal memories  Parietal Lobe: receive and process sensory information from the skin. Help to process information on the body’s position and orientation.

 Frontal Lobe: named for their location at the front of the cerebrum. Integrate info from other parts of the brain and control reasoning, critical thinking, memory and personality. Contains motor areas for precise voluntary movements. The nerves leading from the left and right frontal lobes cross over in the brainstem, so that each side of the brain actually controls muscles on the opposite side of the body.

The Peripheral Nervous System  Consist of nerves that link the brain and spinal cord with the rest of the body, including senses, muscles, glands and internal organs.  Sensory neurons carry information to the CNS  Motor neurons carry information from the CNS to the effectors.  There are two main divisions in the PNS: somatic and autonomic.  Consist of nerves that link the brain and spinal cord with the rest of the body, including senses, muscles, glands and internal organs.  Sensory neurons carry information to the CNS  Motor neurons carry information from the CNS to the effectors.  There are two main divisions in the PNS: somatic and autonomic.

Somatic System  Voluntary control  Includes 12 pairs of cranial nerves, 31 pairs of spinal nerves  Carry information about the external environment through sensory nerves to the CNS.  Voluntary control  Includes 12 pairs of cranial nerves, 31 pairs of spinal nerves  Carry information about the external environment through sensory nerves to the CNS.

The Autonomic System  Involuntary control  Nerves stimulate or inhibit glands, cardiac muscle and smooth muscle.  Maintains homeostasis  Hypothalamus and medulla oblongata control the autonomic nervous system, which has neurons that are bundled together with somatic system neurons in the cranial and spinal nerves.  Has two divisions: sympathetic and parasympathetic.  Involuntary control  Nerves stimulate or inhibit glands, cardiac muscle and smooth muscle.  Maintains homeostasis  Hypothalamus and medulla oblongata control the autonomic nervous system, which has neurons that are bundled together with somatic system neurons in the cranial and spinal nerves.  Has two divisions: sympathetic and parasympathetic.

Sympathetic Nervous System  Typically activated in stressful situations. Often referred to as the fight-or-flight response  Sympathetic neurons release norepinephrine that has an excitatory affect on its target muscles.  Sympathetic nerves trigger the adrenal glands to release epinephrine that further activates the stress response.  Blood pressure increases, heart rate increases.  Typically activated in stressful situations. Often referred to as the fight-or-flight response  Sympathetic neurons release norepinephrine that has an excitatory affect on its target muscles.  Sympathetic nerves trigger the adrenal glands to release epinephrine that further activates the stress response.  Blood pressure increases, heart rate increases.

Parasympathetic Nervous System  Activated when body is calm and at rest.  Restores and conserves energy  Slows heart rate, lowers blood pressure, promotes food digestion  Uses acetylcholine to control organ responses.  Certain drugs can directly affect the sympathetic and parasympathetic systems. i.e. caffeine stimulates the sympathetic nervous system to increase the heart rate and blood pressure.  Activated when body is calm and at rest.  Restores and conserves energy  Slows heart rate, lowers blood pressure, promotes food digestion  Uses acetylcholine to control organ responses.  Certain drugs can directly affect the sympathetic and parasympathetic systems. i.e. caffeine stimulates the sympathetic nervous system to increase the heart rate and blood pressure.

Practice:  Page 369 #1-16  Page 373 #1-5, 11.  Page 369 #1-16  Page 373 #1-5, 11.