Lesson 1: Nervous Tissue

Lesson 1: Nervous Tissue 1. The anatomical subdivisions of the nervous system refer to its physical divisions, such as the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord, while the PNS includes all the nerves and ganglia located outside the CNS. The physiological subdivisions refer to the functional divisions, such as the somatic nervous system (voluntary control of skeletal muscles) and the autonomic nervous system (involuntary control of organs and glands). 2. Neuroglia are support cells in the nervous system, while neurons are the primary functional cells responsible for transmitting signals. Neuroglia provide support, protection, and insulation for neurons. The different types of neuroglia include astrocytes (maintain the blood-brain barrier and regulate ion concentrations), oligodendrocytes (produce myelin in the CNS), Schwann cells (produce myelin in the PNS), microglia (immune defense), and ependymal cells (line the cavities of the CNS and assist in the production of cerebrospinal fluid). 3. A typical neuron consists of a cell body, dendrites, and an axon. The cell body contains the nucleus and other organelles. Dendrites receive signals from other neurons and transmit them towards the cell body. The axon carries signals away from the cell body and transmits them to other cells. The significance of these regions is that they allow for the reception, integration, and transmission of signals within the nervous system. 4. There are three main types of neurons: sensory neurons, motor neurons, and interneurons. Sensory neurons transmit signals from sensory receptors to the CNS. Motor neurons transmit signals from the CNS to muscles or glands. Interneurons connect and transmit signals between other neurons in the CNS. 5. The resting membrane potential is established by the unequal distribution of ions across the cell membrane. This is maintained by Na+/K+ pumps, which actively transport sodium ions out of the cell and potassium ions into the cell. This creates a negative charge inside the cell and a positive charge outside, resulting in a resting membrane potential. 6. The sequence of events during the production of an action potential involves a depolarization phase, where the membrane potential becomes positive, followed by repolarization, where it returns to its negative resting state. The all-or-none law states that once the action potential threshold is reached, it will always occur at full strength. Refractory periods are brief periods of time after an action potential where the neuron cannot generate another action potential, ensuring that signals are propagated in one direction. 7. There are two main types of synapses: electrical and chemical synapses. Electrical synapses allow for the direct flow of electrical current between cells, while chemical synapses involve the release of neurotransmitters to transmit signals between cells. 8. The structural components of a synapse include the presynaptic neuron (sending neuron) and the postsynaptic neuron (receiving neuron), as well as the synaptic cleft (gap between them). When a neurotransmitter carries a signal across a synapse, the presynaptic neuron releases neurotransmitters into the synaptic cleft. These neurotransmitters then bind to receptors on the postsynaptic neuron, initiating a response in the postsynaptic neuron. 9. Some common neurotransmitters include acetylcholine (important in muscle contraction and cognitive function), dopamine (involved in reward and motivation), serotonin (regulates mood and sleep), and gamma-aminobutyric acid (GABA, inhibitory neurotransmitter). Each neurotransmitter has a specific role and function in the nervous system. 10. EPSP (excitatory postsynaptic potential) is a graded potential that depolarizes the postsynaptic neuron, making it more likely to generate an action potential. IPSP (inhibitory postsynaptic potential) is a graded potential that hyperpolarizes the postsynaptic neuron, making it less likely to generate an action potential. EPSPs and IPSPs play a crucial role in determining whether a neuron will fire an action potential or not. Lesson 2: CNS 1. The spinal cord is a long, cylindrical bundle of nerve tissue that extends from the base of the brain to the lower back. It is responsible for transmitting signals between the brain and the rest of the body. It helps in controlling motor functions, relaying sensory information, and coordinating reflexes. 2. The brain and spinal cord are protected by several structures. The skull provides a hard, bony protective covering for the brain, while the vertebral column (spine) protects the spinal cord. The meninges are three protective layers of tissue that surround the brain and spinal cord. These layers are the dura mater (outer layer), arachnoid mater (middle layer), and pia mater (inner layer). 3. Spinal nerves are part of the peripheral nervous system and are responsible for connecting the spinal cord to various parts of the body. They are named based on the region of the spinal cord they originate from. Sensory nerves carry sensory signals from the body to the spinal cord and brain. Motor nerves carry motor signals from the spinal cord and brain to muscles and glands. Mixed nerves contain both sensory and motor fibers. 4. A reflex arc is a neural pathway that controls reflex actions. It consists of several components, including a sensory receptor that detects a stimulus, a sensory neuron that transmits the signal to the spinal cord, an interneuron that relays the signal to the motor neuron, and a motor neuron that sends the response signal to an effector (muscle or gland). Reflexes help maintain homeostasis by allowing the body to quickly and automatically respond to certain stimuli without conscious thought. 5. The major regions of the brain include the cerebrum, cerebellum, and brainstem. The cerebrum is responsible for higher cognitive functions such as thinking, memory, and perception. The cerebellum coordinates movement and balance. The brainstem controls basic functions like breathing and heart rate. 6. The cortex is the outermost layer of the cerebrum and is responsible for higher-level processing. Gyri are the ridges or bumps on the surface of the cerebral cortex, while sulci are the grooves or furrows. Fissures are the deeper grooves that separate the different lobes of the brain. 7. The ventricles of the brain are fluid-filled cavities that produce and circulate cerebrospinal fluid (CSF). CSF helps cushion and protect the brain and spinal cord. There are four ventricles: two lateral ventricles in the cerebral hemispheres, the third ventricle in the diencephalon, and the fourth ventricle between the brainstem and cerebellum. CSF is produced by specialized cells in the ventricles called choroid plexus, and it circulates around the brain and spinal cord, providing nutrients and removing waste products. 8. The basal ganglia are a group of structures in the brain that play a role in coordinating movement and muscle control. They help regulate voluntary movements and are involved in the initiation, execution, and control of motor activities. The limbic system, on the other hand, is involved in emotions, memory, and motivation. It helps regulate our emotional responses and plays a role in forming and storing memories. 9. The major arteries that supply blood to the brain include the internal carotid arteries and the vertebral arteries. The blood-brain barrier is a protective mechanism that regulates the passage of substances from the bloodstream into the brain. It helps protect the brain from harmful substances and maintains a stable environment for proper brain function. 10. The sensory areas of the cerebral cortex receive and process sensory information from the body. The association areas integrate information from different sensory areas and help with higher-level functions like perception, memory, and language. The motor areas are responsible for initiating and controlling voluntary movements. 11. The diencephalon is a part of the brain located between the cerebral hemispheres and the brainstem. It consists of structures like the thalamus, hypothalamus, and pineal gland. The thalamus relays sensory information to the cerebral cortex, the hypothalamus helps regulate body temperature, hunger, and thirst, and the pineal gland produces melatonin, a hormone that regulates sleep-wake cycles. The brainstem is the lower part of the brain that connects the spinal cord to the rest of the brain. It controls vital functions like breathing, heart rate, and consciousness. 12. The cerebellum is a structure located at the back of the brain, under the cerebrum. It is responsible for coordinating and fine-tuning movements, maintaining balance and posture, and controlling muscle tone. It helps with smooth and precise movements, especially those requiring coordination and timing. 13. Cranial nerves are a set of twelve pairs of nerves that originate from the brain and exit the skull through small openings. Each cranial nerve has a specific name, number, and function. For example, the optic nerve (cranial nerve II) is responsible for vision, the facial nerve (cranial nerve VII) controls facial movements and sensation, and the vagus nerve (cranial nerve X) regulates functions of the internal organs. 14. The sensory tracts of the spinal cord transmit information from the body to the brain. Examples include the spinothalamic tract, which carries pain and temperature sensations, and the dorsal columnmedial lemniscus pathway, which transmits touch and proprioception (awareness of body position) sensations. The motor tracts of the spinal cord transmit signals from the brain to the muscles to initiate and control voluntary movements. Examples include the corticospinal tract, which controls voluntary movements of the limbs, and the rubrospinal tract, which helps coordinate muscle movements. The anatomical name of a spinal tract typically indicates its location and the direction of information flow. For example, the spinothalamic tract starts in the spine (spino-) and ends in the thalamus (thalamic), while the corticospinal tract begins in the cerebral cortex (cortico-) and ends in the spinal cord (spinal). 15. Afferent information, or sensory information, enters the spinal cord through the dorsal roots of the spinal nerves. These nerves carry signals from sensory receptors in the body to the spinal cord. Efferent information, or motor information, exits the spinal cord through the ventral roots of the spinal nerves. These nerves carry signals from the spinal cord to the muscles to initiate movement. 16. Ascending tracts in the white matter of the spinal cord transmit sensory information from the body to the brain. Examples include the spinothalamic tract and the dorsal column-medial lemniscus pathway. Descending tracts transmit motor signals from the brain to the spinal cord. Examples include the corticospinal tract and the rubrospinal tract. Ascending tracts are named based on their origin and destination. For example, the spinothalamic tract starts in the spine (spino-) and ends in the thalamus (thalamic). Descending tracts are named based on their origin and destination as well. For example, the corticospinal tract starts in the cerebral cortex (cortico-) and ends in the spinal cord (spinal). The significance of these tracts is that they allow for the transmission of sensory and motor information between the body and the brain. They help us perceive and respond to stimuli, initiate and control movements, and maintain overall bodily function. Lesson 3: Sensory Pathways & Somatic NS 1. Sensation refers to the process of detecting and perceiving stimuli from the environment or within the body. It involves the conversion of physical or chemical stimuli into electrical signals that can be interpreted by the brain. 2. There are different categories of sensory receptors that detect different types of stimuli. These include mechanoreceptors (respond to mechanical stimuli such as pressure and touch), thermoreceptors (detect temperature changes), nociceptors (sensitive to pain), photoreceptors (respond to light), and chemoreceptors (detect chemical changes). Visceral afferent pathways transmit sensory information from internal organs to the central nervous system (CNS). These pathways detect sensations related to the internal organs, such as pain or fullness in the stomach. Sensory afferent pathways, on the other hand, transmit sensory information from the skin, muscles, and joints to the CNS. These pathways detect sensations related to touch, pressure, temperature, and pain on the body's surface. Lesson 4: Autonomic NS & Higher Order Functions 1. The somatic nervous system controls voluntary movements and actions, while the autonomic nervous system controls involuntary actions. Structurally, the somatic system consists of a single neuron pathway from the central nervous system to the target muscle, while the autonomic system consists of a twoneuron pathway with a ganglion in between. 2. The principal structural features of the autonomic nervous system include the sympathetic and parasympathetic divisions, ganglia (clusters of nerve cell bodies), and the connections to various organs and tissues. 3. The autonomic nervous system has preganglionic and postganglionic neurons. Preganglionic neurons originate in the CNS and synapse with postganglionic neurons in the autonomic ganglia. Postganglionic neurons then extend to target organs or tissues. 4. The sympathetic division of the autonomic nervous system prepares the body for fight or flight responses, while the parasympathetic division promotes rest and digestion. Sympathetic neurons originate from the thoracic and lumbar regions of the spinal cord, while parasympathetic neurons originate from the cranial and sacral regions. Sympathetic neurotransmitters include norepinephrine, while parasympathetic neurotransmitters include acetylcholine. 5. The autonomic nervous system is controlled by various levels of integration, including the spinal cord, brainstem, and higher brain centers. These levels help coordinate and regulate autonomic functions. 6. The sympathetic and parasympathetic divisions have some similarities, such as both being part of the autonomic nervous system and having two-neuron pathways. However, they differ in terms of the regions of the CNS they originate from, their physiological effects, and the neurotransmitters they release. 7. The autonomic nervous system uses different neurotransmitters and receptors. Examples include norepinephrine and acetylcholine as neurotransmitters, and adrenergic and cholinergic receptors as their corresponding receptors. These receptors play a significant role in regulating various physiological processes and can be targeted for medical treatments. 8. The adrenal glands are closely related to the sympathetic nervous system. The inner part of the adrenal gland, called the adrenal medulla, is actually a modified sympathetic ganglion. It releases hormones like epinephrine (adrenaline) and norepinephrine directly into the bloodstream in response to sympathetic stimulation. These hormones help prepare the body for fight or flight responses. 9. Autonomic reflexes are automatic responses that occur without conscious control. They are mediated by the autonomic nervous system and help regulate various physiological processes such as heart rate, digestion, and blood pressure. Examples of autonomic reflexes include the pupillary light reflex and the baroreceptor reflex. 10. The major functional areas of the cerebral cortex include the motor cortex, sensory cortex, and association areas. The motor cortex controls voluntary movements, while the sensory cortex receives and processes sensory information from various body parts. The association areas of the cerebral cortex are involved in higher cognitive functions such as memory, language, and problem-solving. 11. The diencephalon is a region in the brain that includes the thalamus and hypothalamus. The thalamus acts as a relay station for sensory information, while the hypothalamus regulates various homeostatic functions like body temperature, hunger, and thirst. The basal nuclei are clusters of neurons deep within the brain that help control movement and posture. The limbic system is a collection of brain structures involved in emotions, memory, and motivation. The reticular activating system is a network of neurons that helps regulate arousal and consciousness. 12. The basis for memory involves the formation and storage of neural connections in the brain. Shortterm memory involves temporary changes in neural activity, while long-term memory involves more permanent changes in the strength and structure of these connections. Arousal is regulated by the reticular activating system, which helps maintain wakefulness and alertness. Behavior patterns developed in the brain are influenced by a combination of genetic factors, environmental influences, and learning. Higher order functions, such as language, problem-solving, and decision-making, involve complex interactions between different regions of the brain and are essential for cognitive functioning.