DP2 Roles of Midbrain, Hindbrain, Forebrain, and Cerebral Cortex PDF

UNIT ONE AREA OF STUDY 2 OUTCOME 2 How are mental processes and behaviour influenced by the brain?​ OUTCOME 2 How are mental processes and behaviour influenced by the brain?  DP2 The roles of the hindbrain, midbrain and forebrain, including the cerebral cortex, in behaviour and me...

UNIT ONE AREA OF STUDY 2 OUTCOME 2 How are mental processes and behaviour influenced by the brain?​ OUTCOME 2 How are mental processes and behaviour influenced by the brain?  DP2 The roles of the hindbrain, midbrain and forebrain, including the cerebral cortex, in behaviour and mental processes Overview of the nervous system  Before delving into the divisions of the nervous system, the central and peripheral nervous systems, consider the cells that these comprise – neurons! The role of neurons  A neuron is a single nerve cell. The human nervous system consists of billions of neurons, which form neural pathways.  In these neural pathways neurons link up to transmit information throughout the body.  Neurons can be considered the building blocks of the nervous system; without them the nervous system could not function.  All neurons do not carry out the same role. Many have specialised functions such as receiving and transmitting information between different neurons and sending information to the cells and muscles of the brain. Structure of the neuron Important terms: Dendrites Soma or cell body Axon Myelin Axon terminals Synapses Neurotransmitters View via Clickview (5 minutes): https://tinyurl.com/pkrdemhf Neuron: The structural and functional unit of the nervous system (Make notes on the key terms above as you view.)  Structure of a Dendrites:  A neuron can have hundreds or thousands of dendrites that look like branches coming off the soma  Dendrites receive information from other neurons, which they carry from the synapse to the soma neuron  Some dendrites also contain dendritic spines, which are additional projections off the dendrite that can also receive information from other neurons  Dendrites and dendritic spines allow one neuron to potentially have thousands of interactions with other neurons. Soma or cell body:  The soma receives the information from the dendrites which then passes down the axon  The largest part of the neuron  It can be considered the coordinating centre of the nerve cell. It controls the metabolism and maintenance of the neuron. Axon:  Transmits signals, allowing the neuron to send information to multiple other cells. The signals that travel along the axon are often referred to as electrical messages, nerve impulses or action potentials. Myelin:  Covering the axons in the human body is a fatty substance called myelin  It is like a form of insulation that helps speed up information transmission in the nervous system. Activity: Model of a neurons 5 Structure of a neuron Axon terminals, synapses and neurotransmitters:  The information transmitted through a neuron always travels in the same direction  Axon terminals store and release a chemical called a neurotransmitter. This chemical messenger takes the information from one neuron to be transmitted to another. This occurs across a gap between neurons referred to as the synapse. Activity: Complete worksheet ‘Neural components and neural transmission’ Types of neurons Sensory neurons Motor neurons  Receive and carry  Carry messages from the CNS to the sensory cells in the skeletal muscles, organs information and glands to stimulate activity. received from  Enables muscles to move so we can both the internal walk and speak and external  Cause glands to secrete chemicals environment  Helps control the function of internal  Main role is to organs. help us sense and monitor changes  Some sensory neurons transmit information directly to the Interneurons spinal cord (to  Create connections between enable the spinal reflex) sensory and motor neurons,  and relay messages from one Sensory neurons type of neuron to another have specialised type of neuron. functions and will  They exist only in the central only respond to a 7 particular type of nervous system (brain and The nervous system  The human nervous system is responsible for all aspects of what we think, feel and do.  Main roles are to receive, process and coordinate a response to information.  Enables the brain to obtain information about what’s going on inside and outside the body.  Vast network of nerve cells (neurons) distributed throughout the body.  There are two main branches of the nervous system: the central nervous system (CNS) and the peripheral nervous system (PNS).  The CNS is composed of the brain and spinal cord, while the PNS comprises all the neurons outside the brain and spinal cord. 8 The central nervous system  The central nervous system (CNS) is so called because of the central position of the brain and spinal cord within the body.  CNS has its own ‘protective armour’ – skull which protects the brain and vertebral column which protects the spinal cord.  The main function of the CNS is to receive information from the PNS, process this information and activate the appropriate area of the body required to respond.  (The brain will be discussed later.)  The spinal cord is a tightly packed column of nerves that extends from the base of the brain (brainstem), down to the lumbar region of the spinal cord.  The spinal cord’s main function is to carry sensory and motor information between the brain and periphery.  The spinal cord transmits sensory information that it has received from the PNS and passes it upwards into the brain, and sends the information received from the brain downwards via the PNS to the relevant organs, glands and muscles of the body so they can carry out the required bodily functions. 9 The peripheral nervous system  The peripheral nervous system (PNS) refers to all the nerves located outside the CNS.  Its role is just as important as the CNS. It is responsible for relaying information from the sense organs, muscles and glands regarding changes in the external and internal environments and delivering this information to the CNS, where a decision regarding bodily response can be made.  The PNS has two subdivisions: the somatic nervous system and the autonomic nervous system. Somatic nervous system:  The role of the somatic nervous system is to carry sensory information to the CNS and transmit information from the CNS.  Sensory neurons respond to information that is detected by sensory receptors at sites around the body i.e., muscles, joints, tendons and the skin. When information is detected, such as change in temperature, it is relayed along sensory neural pathways to the spinal cord and brain. Motor neurons are then activated as the brain seeks to initiate a response, such as the movement of a limb in the body. This information is sent from the brain down motor neural pathways to the relevant muscles to bring about the response. 10 Autonomic nervous system:  The autonomic nervous system is a network of neurons within the PNS that receives information from the CNS and acts to control a range of internal organs and glands. This is done unconsciously; the actions are involuntary i.e., digestion, breathing, heartbeat and perspiration.  There are two subdivisions of the autonomic nervous system: the sympathetic nervous system and the parasympathetic nervous system. Sympathetic nervous system  The sympathetic nervous system activates what is often termed the fight-fight-or-freeze response. This is the body’s rapid, involuntary response to dangerous or stressful situations, which includes raising your heart rate and directing blood to your major muscle groups. Parasympathetic nervous system  The parasympathetic nervous system, on the other hand, activates what is often termed the rest and digest response, which is a range of actions that essentially undo the work of the sympathetic nervous system after a stressful situation. This includes actions such as slowing the Activity: Nervous system ‘cut and heart rate, constricting the pupils and redirecting blood flow paste’ 11 back to intestinal activity to assist in digestion. Regions of the brain Hindbrain Midbrain Forebrain Cerebral cortex THE BRAIN IS DIVIDED INTO FOUR MAJOR REGIONS: THE HINDBRAIN, MIDBRAIN, FOREBRAIN AND CEREBRAL CORTEX View Video 5B-1 Regions of the brain (8 minutes) (Cambridge Chapter 5 The hindbrain – Cerebellum, Medulla oblongata, Pons The hindbrain Activity: Complete ‘Summarising Brain Areas’ table CEREBELLUM MEDULLA OBLONGATA PONS  Involved in a range of bodily Continuation of the spinal cord. Located above the medulla functions, such as coordinating oblongata and below the voluntary movements, balance, Control centre for many autonomic bodily functions midbrain. posture and movements associated with speech and vision. such as swallowing, breathing, Involved in sleep, dreaming Some involvement in learning and heart rate, blood pressure, and arousal from sleep memory. vomiting, salivating, coughing (waking), facial expressions  Ensures movement is smooth and and sneezing. and learning. well-coordinated when multiple Occur automatically, essential Helps control breathing and muscle groups required. for survival. some coordination.  Damage can lead to issues with Damage to medulla can be Acts as a ‘bridge’ connecting balance, challenges associated fatal e.g., blow to the back of the cerebral cortex and with detecting visual motion and the head or lead to severe cerebellum. loss of muscle coordination. health problems. 15 The midbrain – Substantia nigra, Reticular formation  The midbrain  The midbrain is at the centre of the brain and sits at the topmost part of the brainstem. It works to connect the upper and lower areas of the brain.  The midbrain is involved in auditory and visual processing and plays a big role in motor control, pain inhibition and reward-based learning patterns.  Important structures: Substantia nigra and reticular formation. Substantia nigra:  Is one of the largest collections of dopamine-producing neurons in the brain.  Dopamine is a neurotransmitter involved in movement and coordination.  Parkinson’s disease which is characterised by tremors and difficulty with movements, is linked to nerve cell damage in the midbrain. Reticular formation:  The reticular formation is a complex arrangement of neuron clumps, which are connected to a network that runs from the hindbrain to the forebrain.  These neurons play a significant role in maintaining arousal, consciousness and motor control.  Contains a specialised system called the reticular activating system (RAS) which when stimulated, causes alertness and awakening. The groupings of neurons that make up the RAS are ultimately responsible for attention, arousal, control of muscles and the ability to focus.  The RAS filters out unnecessary information, so only the important stuff 17 gets through. The forebrain – Hypothalamus, Thalamus, Cerebrum The forebrain  The largest region of the brain.  Neurons in the forebrain connect with both the midbrain and hindbrain and play an important role in coordinating brain activity.  Involved in a range of bodily functions, as well as learning, memory, thinking and perception.  Important structures: cerebrum, thalamus, hypothalamus, pineal gland, and limbic system. Hypothalamus:  Size of an almond, located under the thalamus.  Involved in connecting the hormonal and nervous systems via the pituitary gland. It regulates the release of many hormones that play a role in maintaining homeostasis (the constant internal environment of the body) through control of bodily temperature, hunger, thirst and sleep.  Part of the limbic system (system of interconnected structures that play a role in how we experience emotions, behaviour control and long-term memory).  Damage to the hypothalamus can lead to issues with controlling body temperature, continuing to feel hungry after eating, problems sleeping and change in libido. Thalamus:  The thalamus has two halves, located side by side but each in a separate hemisphere of the brain.  Located within the forebrain, near the centre of the brain.  Most significant function is to relay information to relevant sections of the cerebral cortex for additional processing. In particular sensory information (except smell) comes via the thalamus, where processing and relay occur.  Plays major role in regulating arousal, with connections to the reticular formation and RAS system. Damage to this area of the brain may cause an individual to go into a coma. 19  Plays a role in attention and assists us in focusing on important information. Helps to filter the vast amount of The forebrain Cerebrum:  The largest part of the forebrain and contains two cerebral hemispheres, which are separate but partially joined by the corpus callosum. (The corpus callosum allows information to be exchanged between the two cerebral hemispheres – a strand of nerve tissue that connects the right and left sides of the brain.)  The cerebrum is responsible for directing the conscious motor activities of the body, as well as receiving and processing a range of sensory information.  The outer layer is referred to as the cerebral cortex. 20 The cerebral cortex The cerebral cortex  Thin layer of neurons that covers the outer region of the cerebrum.  Accounts for approximately half the weight of the brain.  Divided into two hemispheres.  Specific areas dedicated to specific functions, that is, there is localisation of function i.e., the visual cortex is involved in receiving and processing information from the eyes. However, most areas of the cerebral cortex perform a variety of functions.  Forms extensive connections with the brain subcortical areas (areas below it). Thus, plays a role in a range of brain functions including the processing of complex sensory information, the initiation of voluntary movements, language, symbolic thinking and the regulation of emotion.  Three areas: sensory, motor and association areas. - Sensory areas are involved in receiving and processing sensory information. - Motor areas initiate voluntary movement. - Association areas are extraordinarily important as they integrate information from multiple brain regions, facilitating complex cognitive processes such as language, creativity 22 and decision-making. Cerebral hemispheres  Left and right brain hemispheres.  Separated by large groove – longitudinal fissure.  Extend from the front to back of the brain.  They perform many of the same functions but are not identical.  Each hemisphere controls motor and sensory functions on the opposite side of the body i.e., left hemisphere receives sensory information from the right side of the body and controls movement on that side (and vice versa).  The positions of sensory and motor areas are similar for both hemispheres.  Each hemisphere has some specialised functions that are not possessed or controlled to a lesser extent, by the other Complete Activity 4.5 Classifying hemispheric specialisations – this is called hemispheric (Jacaranda) specialisation, however both 23 hemispheres play at least some role in all Cortical lobes of the cerebral cortex 25  Frontal lobe  The frontal lobe is located in the upper forward half of both the left and right cerebral hemispheres.  Three key areas: prefrontal cortex, premotor cortex and primary motor cortex.  Prefrontal cortex associated with sophisticated mental abilities such as reasoning, planning, problem- solving, decision making and symbolic thinking. Also involved in regulation of emotions, self- awareness and aspects of personality such as initiating appropriate and inhibiting inappropriate behaviour. Psychologists refer to this part of the frontal lobe as having an ‘executive’ role in all our thinking, feeling and behaving. This is because it coordinates many of the functions of the other lobes and determines our responses. Primary motor cortex:  Runs along back of frontal lobe.  Involved in controlling voluntary bodily movements through control of skeletal muscles.  Primary motor cortex in left hemisphere controls the muscles in right side of body.  A different area along the primary motor cortex is involved with the movement of specific body parts. The amount of cortex devoted to a particular body part corresponds to the complexity of its movements.  The prefrontal cortex is involved in planning a motor sequence for voluntary movement. It sends the message to the premotor cortex which prepares the information to be sent to the primary motor cortex. The primary motor cortex then sends messages to the skeletal muscles. Broca’s area:  Left hemisphere next to primary motor cortex  Contributes to clear and fluent speech by coordinating movements of muscles involved.  Broca’s area sends and receives messages from other areas of the brain involved in language e.g., those that assist with understanding the meaning of words, which contributes to overall speech production. 26  Temporal lobe  Located below the frontal and parietal lobes of the brain.  Sits just above the ear and plays a significant role in receiving and processing sounds from the ears, as well as memory, emotional responses to sensory information and some visual perception, such as our ability to recognise faces and identify objects. Primary auditory cortex:  The primary auditory cortex, assists in identifying and responding to sound, with different parts responding to different sounds i.e., high or low pitch. Wernicke’s area:  Wernicke’s area is located in the left temporal lobe.  Plays a critical role in understanding the sounds involved in speech.  Role in speech production and has connections to Broca’s area in the frontal lobe. 27 Parietal lobe  Located behind frontal lobe but does not extend all the way to back of brain.  This lobe comprises areas involved in spatial awareness, spatial reasoning, attention and receiving and processing somatosensory information. Primary somatosensory cortex:  Receives and processes sensory information from a range of body areas, including arms, feet, legs, lips, tongue and genitals.  Right primary somatosensory cortex processes information from left side of the body (and vice versa).  Areas more sensitive are devoted more space in the primary somatosensory cortex i.e., fingers allocated more space than the knee. Complete Homunculus Mapping practical activity 28 Occipital lobe  Located at the rear of each cerebral hemisphere.  Primarily involved in vision. Primary visual cortex:  Receives and processes visual information sensory receptors in the retina of both eyes (left half of each eye sending information to the primary visual cortex in the left occipital lobe and the right half of each eye sending information to the right occipital lobe).  Neurons in the primary visual cortex and surrounding ‘secondary’ visual areas are specialised to respond to different features of visual information, such features as:  orientation (‘direction’) of a line  edges, shape (‘forms’)  motion and colour.  Some neurons respond to specific features (e.g. shape or colour), while other neurons respond to two or more features (e.g. shape and colour). 29 Further activities:  Activity 4.6 Summarising the cerebral cortex and its cortical lobes (Jacaranda)  Activity 4.7 Functions of the lobes (Jacaranda)  Activity 4.8 Assembling a jigsaw of the brain (Jacaranda)